Organized by - Comité des Plastiques en Agriculture

Transcription

NEW
AGRICULTURAL
TECHNOLCffilES
• 1 9
nd
2
9
4«
INTERNATIONAL CONGRESS
ON NEW AGRICULTURAL
TECHNOLOGIES
Puerto Vallarla, México
(Nuevo Vallaría, Nayarit, México)
April 20 to 23
ORGANIZED BY:
m
(
)
QftCcpn
nam L. i li
exportadora de plásticos
agrícolas, s. a. de c. v.
Government
of the State
of Nayarit
é,AQU
A FINI,
oAp
S. A. DE C. V.
I IQUID CARBONIC
FIBRAS
PLASTICAS
!>f.MÍ XICOS
. A díC V.
Organized by:
Honorary President
Rigoberto Ochoa Zaragoza
Gobernador Constitucional
del Estado de Nayarit, México
President
Technical Secretary
Administrative Secretary
Member
Member
Member
Member
Lic. J u a n J . García de Alba B.
Dr. Gilberto Gómez Priego
Miss. Josefina Monraz
Lic. Mario Palacios Kaim
Ing. Silvestre Pérez González
Ing. Jacinto García Martínez
Lic. Guillermo F e r n á n d e z
Presentation
/
t is very gratifying to see how agricultural
technology is
spreading at an especially rapid rate which only three or four
years ago would have been unheard of Last year's
First
International
Congress of New Agricultural
Technologies left a seed which has borne fruits in the fields of visionary growers
who improved their crops; it also offered them the chance to achieve
new goals and a more promising
future.
This is why the government of the State of Nayarit
and the
organizing
companies
decided to organize this Second Congress,
with the firm intention of contributing in a real and feasible way to
technologize the Mexican grower.
We feel especially grateful to all our national and
international
speakers who, with excellent disposition, have shared their work and
knowledge with all those aspiring to become better growers.
We hope that the conferences as well as the exchange of ideas and
expertise among the participants
of this Second
International
Congress of Agricultural
Technologies,
serve to achieve a better
agriculture and a more productive Mexico.
Welcome!
Lie. Juan
J. Garcia
de Alba
President of the Organizing
B.
Committee
O r g a n i z e d by:
«ttcon
)MW1
)
- i
II
Tri-Cal, Inc.
Exportadora de Plásticos Agrícolas,
S. A. de C. V.
M R . MARK MCCASLIN
1029 Railroad St.
Corona, CA. 91720, U.S.A.
b (909) 737-6960
Fax (909) 734-1154
L i c . J U A N J . GARCÍA DE A L B A B .
Av. Circuito Madrigal N s 1736
Zapopan, Jalisco, México
« (3) 642 7542
Fax (3) 642 7342
ié
AQUAFIM,
S. A. DE c . v . e ^
Aquafim, S. A. de C. V.
Liquid Carbonic de México,
S. A. de C. V.
I N G . SILVESTRE P É R E Z GONZÁLEZ
Veracruz Ng 317 Poniente
Hermosillo, Sonora, México
« (62) 15 15 57
Fax (62) 16 28 52
L i c . GUILLERMO FERNÁNDEZ
Biol. Maximino Martínez Ng 3804
Colonia San Salvador Xochimanca
México, D. F. 02870
» (5) 341 2197
Fax (5) 396 8138
FIBRAS
PLASTICAS
Fibras Plásticas,
S. A. de C. V.
L i c . M A R I O PALACIOS KAIM
Calle 1 A N2 92 y 29
Colonia San José de la Escalera
« (5) 391 9175
Fax (5) 392 0819
Conferences
Index
World
plasticulture
Speaker:
SR. PHILIPPE PRINTZ
President of Comité
Internacional des Plastiques
en Agriculture
Paris, France
Design alternatives
and selection
of localized irrigation
systems
Speaker:
I N G . D A N I E L VELÁZQUEZ DUARTE
Aquafim, S. A. de C. V.
Hermosillo, Sonora, México
Sap analysis and
fertigation
management in horticulture
with
plastic
mulch
Speaker:
D R . HÉCTOR BURGUEÑO
Bursag, S. A. de C. V.
Culiacán, Sinaloa, México
Cultural vector control of virus:
plant louse and white fly
Speaker:
M . C . OCTAVIO Pozo CAMPODÓNICO
Instituto Nacional
de Investigaciones Forestales
y Agropecuarias
Tampico, Tamaulipas, México
Improvement and control
of indoor
horticulture
Speaker:
D R . J O S É L Ó P E Z GÁLVEZ
Chief of "Las Palmerillas"
Experimental Station
Almería, España
Corn plasticulture
Speaker:
in France
ING. M . L E D U J E A N
Centre National Du Machinisme
Agricole du Genie Rural Des Eaux
et des Fonets
Francia
Web vegetable
as competitiones
Speaker:
cultivation
tools
ING. ALEJANDRO GÁLVEZ
Invernamex
Mexico
Automatization
and nutrition
Speaker:
of irrigation
equipments
ING. A V I IVANIR
Chief of Training and Service in
Latin America, Motorola of Israel
Jerusalem, Israel
Diseases and soil
Speaker:
solutions
D R . ALBERT O . PAULUS
Plant Pathology University
of California
Riverside, California, U. S. A.
Intensive strawberry
Speaker:
production
D R . EDGAR Q U E R O GUTIÉRREZ
Oganización Bimbo-Frexport
Zamora, Michoacán, México
Solarization
Speaker:
in México
D R . FLORENCIO J I M É N E Z DÍAZ
INIFAP
Torreón, Coahuila, México
Drip irrigation and
in citrics and vines
Speaker:
microspraying
B E N A M I BRAVDO
PH. D. Chief of the Division
for Outside Studies of Horticulture
and Fruit Growing,
Faculty of Agriculture,
Hebrew University of Jerusalem
Jerusalem, Israel
Intensification
and
conduction
of tomato
cultivation
Speaker:
D R . RODRIGUE N E L S O N VIGOUROUX
Agro Industrias Campus
Tequisquiapan, Querétaro, México
A grower's attitude on
of new
technologies
Speaker:
aplication
S R . SALVADOR GARCÍA GUTIÉRREZ
San Quintín, Baja California Norte,
México
World plasticulture
M R . PHILIPPE PRINTZ
Comité Internacional des
Plastiques en Agriculture
MR.
J . he idea of using plastic materials in
agriculture first appeared some 50 years
ago. Since then, much progress has been
made in the utilization, conception and
materials used, which in turn has brought
about substantial plastic consumption
in this field. This progress continues
with new applications in many countries.
New national committees have been
created: Pakistan 1992, Israel 1993,
PHILIPPE
PRINTZ
Algeria 1994...
Applications vary from one country to
another, depending upon whether climate
conditions create a stronger need for
saving water, for protection against the
environment, or to strive for precocity
and protection of crops after harvest.
These techniques do not necessarily
apply in every country.
Some global statistics on world plasticulture
Mulching
Surface / areas! ha.
Tonnage (t)
Regions
Min.
Max.
Min.
Max.
Western Europe
250,000
300,000
60,000
75,000
Eastern Europe
8,000
10,000
2,000
2,500
Africa/Middle East
8,000
10,000
2,000
2,500
America
180,000
200,000
45,000
50,000
Asia/Oceania
3'000,000
3'500,000
300,000
350,000
World total
3'446,000
4020,000
409,000
480,000
15
World
plasticulture
Regions
Greenhouses
S urface / areas / ha.
Tonnage (t)
PEbd
PVC
115,000
1,500
30,000
Min.
Max.
Western Europe
Eastern Europe
61,000
20,000
64,000
22,000
Africa/Middle East
15,000
8,000
17,000
10,000
25,000
15,000
182,000
286,000
190,000
200,000
303,000
385,000
America
Asia/Oceania
World total
USA
Canada
100,000
3,500 ha.
500 ha.
Floating covers
Europe 30 000 ha
(against only 25,000 in 1987)
USA 6,000 acres
Microtunnels
54,000 in Western Europe
27,000 of which are in Italy and Spain
Storage in silos
145-155 000 tons in Europe
These numbers attest to the economical
and social importance of plastic use. Let's
examine more closely the application of
plastic in some countries which will serve
as examples.
MR.
PHILIPPE
PRINTZ
Plasticulture in México
Key figures:
ha
1. Mulching
2. Low tunnels
3. Walk-in tunnels
4. Wind-breaks
5. Greenhouses: seedlings
6. Greenhouses: ornamentals
7. Anti-hail nets
8. Micro-spraying
9. Direct covers
10. Drip irrigation orchards
11. Drip irrigation vegetables
12. Soil disinfection
Total
3,982
3,790
113
100
91.4
532.72
4,794.24
11,135.00
17.28
18.300
10,108.5
520.0
53,484.14
%
7.44
7.09
0.21
0.91
0.17
1.00
8.96
20.82
0.032
34.2
18.69
0.97
100.0
t
1,392.97
1,664.90
361.6
28.0
298.88
1,658.3
3,472.81
9,464.75
7.08
14,460.05
980.96
178.6
33,968.81
%
4.10
4.90
1.06
0.08
0.88
4.88
10.22
27.66
0.021
42.57
2.89
0.53
100.0
Principal material used: polyethylene.
Films: 60,000 t.
Strings: 18,000 t.
Main tendencies:
Tubes and hoses.
- Increase in mulched surfaces.
In the above applications, polyethylene
- Increase in floating covers (at present accounts for 95,000 t; PVC for 45,000
700 ha.) We noticed, as in many other t; polypropylene for 45,000 t; others,
countries, the efficiency of these products 10,000 t.
in fighting against crop enemies.
Undoubtedly, plastic films are the most
significant category, but it should be borne
— Increase in drip irrigation.
— Progress in the use of plastics for soil in mind that part of these films are used
in silos, as covers (25,000 t) and as
sterilization (520 ha.)
stretchable wraps for round bulks of fodder
(2,000 t). 10,000 t are used as films for
Plasticulture in France
microtunnels (lower t h a n 1 m high).
Key figures: 4.5 million tons of plastics Between 14,000 and 18,0001 are used as
consumed each year, 170,00 tons of which mulch, 5,000 t of which are photodegrapertain to specific agricultural applica- dable for corn growing. 7,5001 are used in
production greenhouses and plantule
tions divided between:
17
World
plasticulture
production. Perforated films are used as
direct covers.
Principal horticulture crops benefiting
from plastic use:
Greenhouse: tomato, cucumber, roses
and flowers, lettuce.
Microtunnel:
strawberries, melon,
carrot, red valerian.
In the field, under mulch and floating
covers: lettuce, melon, radish.
Greenhouse films have a thermal effect
giving plants maximum protection against
spring frost. These long-life films serve
for three or four crop cycles (films are
placed at the end of summer to avoid UV
degradation, especially during the months
with highest insolation). Thickness ranges
from 180 to 200 mm.
Products are labeled according to
regulations, so the consumer may identify
them.
Microtunnel films have a short life. To
avoid heating during spring, they are
frequently perforated with knives or
heating devises to allow better ventilation.
Thus, they cannot be used afterwards.
These films are traditionally 80 mm thick.
The introduction of LLDPE (Linear Low
Density Polyethylene) brought about
thinner films with the same mechanical
properties.
Thickness in these films may vary
between 40 to 80 jam, though 60 is the
usual. Thicker films afforded the best
results as far as precocity (since they have
the strongest thermal effect.)
PVC films were once used for films, but
their utilization is declining for several
reasons: they're more expensive than PE
based products, less resistant to the wind,
and cause disposal problems.
There microtunnel films are also
regulated.
Mulch films are very diverse in nature
(color, thickness), but they have two main
18
objectives: black or opaque films are used
to fight weeds, and clear films are used to
heat the soil. Crops growing outside the
soil, which are becoming increasingly
important in greenhouses, require films
to reflect the light in favor of better
photosynthesis.
Photodegradable films aren't used save
for corn crops. However several hundreds
of hectares of industrial tomatoes are
covered with these films. Biodegradable
films are still unavailable in the market.
New techniques under development:
- The use of stretchable films to wrap
round fodder bulks. This technique is
appropriate for animal breeding (goats
and sheep) in small farms, and requires
little investment.
- Solar sterilization (solarization) of
soil during summer seasons to avoid
applying chemical agents which may leave
traces in the vegetables grown later.
- Floating non-webbed covers to avoid
attacks from certain viral vectors. The
idea is to find alternatives to treatments
which aren't effective enough in spite of
repeated (and costly) applications, and to
guarantee the consumer the absence of
chemical traces.
Plasticulture in Spain
Key figures:
Total plastic consumption in the
country: 2,200,0001.
Agricultural plastics represent 7.3%
(162,000 t).
In order of importance:
Films (greenhouses, mulch, tunnels,
ponds), 36%
Irrigation, 30%
Materials used:
LDPE, 51%; PVC 23% (irrigation);
HDPE for boxes, screens; PP, 14,500 t.
Main surfaces:
MR.
Mulch: + than 100,000 ha.
Greenhouses: 28,500 ha. Principal
crops: pepper, tomato, cucumber, melon
and watermelon. 2,000 ha are solely
dedicated to flowers, 300 of which are in
the Canary Islands.
Microtunnels: 17,000 ha (much of this
surface is inside greenhouses to speed
melon and especially watermelon crops).
It is in Andalucía (Almería region, in
southern Spain) where the largest surface
cultivated under plastic films is located.
Films most frequently used:
Greenhouses: 90% PE long-lasting
films. (The proportion in Andalucía is
70% "regular" and 20% thermal, and the
reverse proportion prevails in the Murcia
region.)
Long lasting films are 180 to 200 pm
thick. EVA films are used in cooler
climates and with less sunshine than those
in the southern part of the country. HDPE
94 g/m2 shades are particularly spreading
in the Canary Islands (1,500 ha). 40-50
pm films are used for soil sterilization.
Microtunnels (40-50cm wideandhigh):
have covered a stable amount of land for
some years now. Films are between 25
and 75 mm thick.
Mulch: 55% of mulched surface is
dedicated to cotton, where 12 pm films are
applied. In the case of melon and tomato,
PE films or mixes with LLDPE are used.
Thickness ranges between 25 and 40 pm
(i.e., 100-120 kg/ha). In asparagus crops
(6-7,000 ha) 30-60 pm films measuring
1.5 m in length are used. This film has a
side soil-filled pleat that avoids lifting due
to wind. The other side is buried at the
base of the bed so this film can be lifted
and replaced whenever necessary. Pepper
crops utilize 50-75 pm films, which are 3
to 4 meters wide.
Irrigation: Represents 30% of agricultural plastic consumption (47,0001). There
PHILIPPE
PRINTZ
are more t h a n 3,025 ha irrigated of
irrigated crops, if we consider all existing
irrigation systems. (650,000 ha are
irrigated with sprinklers and 150,000 ha
are drip-irrigated.)
Pond waterproofing for water storage:
During the past few years, this market
has grown and now represents 5,000 t.
(2,500 of PVC, 1,500 of HDPE, and 1,000
of LDPE. ) It is the answer for regions with
scarce rainfall.
Plasticulture in the
United Kingdom
Key figures:
Greenhouses: 1,200 t of PE films for
1,000 ha of greenhouses.
Microtunnels: 500 t.
Thermal insolation in greenhouses: 6001.
Floating covers: 2,700 t perforated
films, 500 t un-webbed .
Silo storage: 5,8001 of covers, 3,0001 of
bags, 1,300 t of stretchable film.
Wrapping: 8,0001 of PE and 2,0001 of
PET (polyethylene terephtalate)
Water deposits: 1,000 t.
It should be noted that England,
together with Belgium was among the
first countries to adopt stretchable film to
protect fodder balls after harvest. Climate
conditions in these countries make it
difficult to produce hay, while storage in
silos allows production of good quality
fodder which keeps up to one year. This
technique is under development en many
countries.
Plasticulture in Germany
Plastics used in agriculture: 150,0001,
of which 45% is PE, 25% PVC, 13% PP,
and 7% PS.
Main application: film for silo storage,
50,0001.
World
plasticulture
Greenhouse films: 400 t. Plastic
greenhouses represent only +/- 15% of
covered land- that is, 600 ha.
Mulch: Mainly for asparagus, cucumber and strawberry (100 ha).
Floating covers: 6,100 ha. Non-webbed
covers are progressing noticeably. They
are also used as protection against cold in
vegetable crops, herbaceous plants and
wood plants.
Plant pots and trays: 360 million units
for potted plants, 110 million for greenhouse plants, 400 million for plantules,
750 million for shrub plants.
Plasticulture in India
Another continent, other techniques,
another culture; the need to feed close to
one million human beings. Plasticulture
in India doesn't have the same bases nor
objectives as in Western Europe or North
America.
Promoting plasticulture is a priority
and there are development centers all
over the country, where experimentation
is under way, especially in the realm of
drip irrigation, sprinkling, mulching
(tomato, potato, tea, strawberry, for yield
increases which have reached 20 to 30%
and water savings between 50 and 70%),
water reserves, undercover crops (only
the first stages of experimentation) and
everything concerning post-harvest.
Two million plastic boxes instead of
wooden boxes have reduced wood
consumption and contributed to protecting
the remaining forests.
Main existing applications:
Hoses (100,000 tPVC)
Outdoor harvest storage (5,0001LDPE)
Greenhouse bags (20,000 t PE)
Principal Actions under Way:
Drip irrigation (3,0001) on an area that
grew from 1,000 ha in 1983 to 26,000 ha
20
in 1992.
Channel waterproofing (10,000 km
already completed).
Plasticulture in Morocco
This North African country essentially
applies plasticulture in greenhouse crops.
Close to 4,500 ha are dedicated to garden
vegetables, and 400 ha to floral crops,
tomato, melon, peppers, string beans,
strawberries and banana.
Though Morocco has a favorable
c l i m a t e , w h e n compared to o t h e r
temperate-climate countries in Europe,
crops here also tend to move to the south.
Cover films, 220 (am thick, last for two
years.
Greenhouse structures sometimes have
double walls to avoid temperature losses
during the winter.
Plasticulture in Japan
Key figures:
In 1989, out of44,800 ha of greenhouses,
only 2,000 were made of glass.
PVC is the most frequently used material to manufacture cover films (historical
reason): 89% of greenhouses are covered
with PVC, as well as 66% of the 54,000 ha
of tunnels.
Conversely, 85% of the 133,000 ha of
mulched crops, use PE.
Once more, garden vegetables occupy
the greatest share of land: strawberries
15%, c u c u m b e r s 13%, melons 13%,
tomatoes 11%.
Regulations: a tendency;
quality insurance
In order to help growers make the right
choice, several countries have established
regulations in close collaboration with
MR.
manufacturers, distributors and users.
These regulations help define adequacy
for a given application. Products conforming to regulations can be labeled when
there exists a qualification certificate (or
quality label).
Periodical control during the manufacturing process should be carried out by
the manufacturer. Additional controls
carried out by an independent laboratory
will insure that labeled products truly
conform to regulations.
Though it is true that this research
generates costs and that labeled products
are a little more expensive than standard
products, in many cases, growers can't
afford the risk of using u n r e l i a b l e
materials.
At present, work is being done in
Europe to establish a European regulation
t h a t will replace existing domestic
regulations.
Plastics and the environment
Sometimes plastics are criticized for
environmental reasons. It's interesting
to confirm, however, that these materials
are important agents protecting the
quality of the environment.
Witness to this are mulch films which
make it possible to avoid chemical
herbicides altogether and save water by
impeding soil evaporation, which also has
a bearing on efficient fertilizer use, since
there is no washing.
Mulches are commonly utilized together with drip irrigation, the best system
to optimize low water resources.
Another example are films used for
soil heating and sterilization which
suppresses or at least decreases pathogen
fungus, nematode and weed populations.
Other witnesses are non-webbed covers
which keep plant lice, and other pests
PHILIPPE
PRINTZ
away from plants, and so avoid virus
transmission or the effects of direct
parasites which affect yield and quality.
These covers have made cultivation
possible, under plague conditions so severe
that even agricultural spraying wouldn't
help.
Films used for solarization should also
be mentioned, since they avoid chemical
disinfectants.
Agricultural plastic recycling represents several problems due to its inherent
characteristics: wide diversity of materials
and applications (and, evidently, geographical dispersal), as well as degree to
which it becomes soiled.
Nobody questions these factors, but
research is under way to propose simple
and cost-efficient solutions that will allow
an environmentally sensible means of
disposal.
Until now, in many countries the
garbage dump continues to provide the
most widely used solution, since it is the
cheapest and closest to the crops. This is
certainly not the most ecological answer.
(Can't something else be done with plastics
instead of just burying them in some
landfill?) Soon in many countries this will
no longer be a feasible practice, since laws
have been emitted in several nations
(France, Germany), limiting the tons of
waste that can go into a landfill.
In the short term, the most satisfactory
solution, intellectually speaking, seems
to be recycling the material. Old films
could be used to manufacture second
generation products (garbage bags, films
for silo storage).
In practice, however, this solution must
face present economical considerations,
especially the low price of raw resin.
Nevertheless, recycling is the solution for
thick (100 pm) films. It is believed that in
Europe today, 8,000 t of PE agricultural
21
World
plasticulture
films are being recycled. France accounts
for an important share of this recycled
plastic.
Thinner films used for mulch and
microtunnels (which become extremely
soiled due to their thickness and contact
with the ground) are better eliminated by
incineration, whether in domestic waste
incinerating plants which recover energy,
or in plants with a high energy consumption, such as cement manufacturers.
Burning in the open field evidently, is not
part of the solution.
Plasticulture: more perspectives
for the future
Thanks to national organizations
22
(Comepa in Mexico, CPA in France, GKI
in Germany, etc.) and to all the research
centers currently working in this field,
the dialog between growers and manufacturers continues.
Progress has been achieved both in the
manufacture of the products, and knowledge of plant physiology.
The products of the future will undoubtedly be more sophisticated: films selectively absorbing certain radiations,
retaining infrared rays, films serving as a
barrier for certain gases conditioning
fruits and vegetables; degradable films,
etcetera.
Information on the latest in products
a n d t e c h n i q u e s s h o u l d be quickly
circulated.
Design alternatives
and selection
of localized
irrigation systems
ING. DANIEL VELÂZQUEZ DUARTE
A q u a f i m , S. A. d e C. V.
INO.
Introduction
A V a t e r is an increasingly scarce resource,
not only in quantity, but also quality.
Since growers are the principal water
consumers, they're obligated to use it in
the most efficient way possible, within the
economical considerations every production activity entails.
Even in areas considered to have a
healthy supply of irrigation water, illmanagement can bring about contamination problems which will have negative
repercussions on the crops, mainly those
located in lower areas.
Localized irrigation is a system allowing
application of filtered water and chemicals
to the soil through a network of tubes and
other specialized e q u i p m e n t called
emitters. Water is taken to the source of
each plant, eliminating carrying losses
Irrigation method
Localized irrigation (drip and micro-spray)
Main spraying systems
Movable irrigation systems
Flood or row irrigation
DANIEL
VELÀZQUEZ
DUARTE
and minimizing evaporation and deep
percolation, without submitting the plants
to extreme conditions.
The objective of localized irrigation
systems, from t h e agronomic and
engineering point of view, is to keep
humidity between the soil saturation level,
a fraction lower than field capacity, around
the radicular area of the plant.
This is why it's important to apply
basic knowledge on water use so systems
can be designed to meet t r u e crop
requirements.
Efficient application
Different irrigation systems allow great
losses in the amount of water used, since
the volume of water applied by each system
varies:
Efficiency %
90-95
80
70
50 or less
25
Design alternatives
and selection of localized irrigation
systems
Project capacity represents the maximum irrigation the system can supply,
which is based upon the critical évapotranspiration forecast of the crop. Maximum water requirements will depend upon
the following:
1. Climate conditions.
2. Crop development.
3. Rain distribution.
4. Soil water retention.
5. Type of crop.
6. Application efficiency.
7. Need for washing.
System uniformity
The uniformity of a localized irrigation
system will depend upon:
- Pressure differences arising in the
hydraulic network due to losses on account
of friction and the topography of the plot.
- Uniform emitter manufacture.
- Number of emitters supplying the
plant.
- Emitter response to changes in water
temperature and pressure.
- Variations in the performance of the
emitter due to possible plugging and/or
aging.
- The effect of the wind when sprayers
or micro-sprayers are in use.
- Efficient manufacture of pressure
regulators when they are the case.
The degree to which each one of these
factors can affect irrigation evenness
has been established by Solomon (1985),
from greatest to lowest importance as
follows:
- Obturations
- Number of emitters supplying the
plant.
- Variation coefficient on the manufacture of the emitter.
- Emitter discharge exponent.
- Emitter sensitivity to temperature.
- Pressure variations.
- Variation coefficient on the manufacture of the pressure regulators.
- Ratio between the loss of load in the
main tube and the irrigating tube.
- A m o u n t of d i f f e r e n t d i a m e t e r s
making up the main line.
Design
The design of a localized irrigation
system consists in detailed specification of
every component and required practices
to establish irrigation, operation and
maintenance calendars. Design implies
an integration of irrigation technology to
an agricultural production system, taking
into account, besides wholly technical
aspects, agronomic, environmental, social
and economical considerations.
The object of designing irrigation is to
achieve efficient water and nutrient
distribution in the crop. The best measure
of efficiency in an irrigation system is a
uniform or even application.
The following are the steps taken in the
design of an irrigation system:
- Selecting the type of system.
- Estimating maximum water and
nutrient demands.
- Selecting the emitter (flow, type and
spacing).
- Selecting irrigation lines (diameter
and thickness).
- D i s t r i b u t i n g t u b e s and m a k i n g
hydraulic calculations.
- Selecting type of filter.
- Selecting product injection equipment.
- Selecting a retro-washing unit (manual or automatic).
- S e l e c t i n g pumping equipment
(centrifugal, vertical, submergible).
PHYSC
IAL !
CHARACTERS
ITC
I
OF UME SOL
I
VOLUME Of
WET SOIL
FET
iTR
lRG
tATKDN
REQUERM
I ENT5 BY
PHENOLOGC
IAL
STAGE AN AT
MAX
M
IUM DEMAND
HYDRAUUC
CALCULATO
INS
1
CUMATE
[
CALCULADON
27
Design alternatives
systems
Technical viability study
For each one of the design alternatives,
it's necessary to establish whether or not
the system poses a practical irrigation
solution by identifying its advantages and
disadvantages such as:
- Water application and humidity
distribution in the soil.
- Supply and quality of the water.
- Cultural operations.
- Supply and type of energy.
- Labor requirements, including level
of training.
- Engineering services availability.
- System reliability.
- Natural resource and environment
conservation.
Cost analysis
The next step is to estimate the
following costs for every system:
- Initial investment.
- Fixed annual cost.
- Annual operating expenses.
- Total annual cost.
This analysis should consider, among
its annual operating expenses, the savings
a localized irrigation system offers in
agronomic and economical advantages.
Perhaps the most important of these is
that irrigation doesn't interfere at all with
activities like cultivating, applying
chemical or organic products, harvesting
and watering at the same time, etcetera.
Besides, the appearance of unwanted
plants among the rows is inhibited, thereby
reducing cultivation activities. This of
course, is of immediate economical
consequence, since crop maintenance
r e q u i r e s a r e d u c e d i n v e s t m e n t in
equipment and labor.
28
Estimate of required yield increase
to cover irrigation costs
To determine if the irrigation system is
productive from the economical point of
view, we must first calculate the increase
in yield to pay for the irrigation system.
This is difficult since it entails estimating
the unit market price of the product under
cultivation.
Distribution of the tubes
and hydraulic calculations
Once the right kind of emitter has been
selected and the load it will be working
under is determined, the next step is to
decide the distribution of the tubes in the
system. Generally, this process begins with
defining the placement of the main
watering tubes and finally the supply
tubes. This depends upon:
- The distribution of the crop.
- Topography.
- Location of the water source.
The supply should be calculated based
upon certain economical criteria such as
optimum diameter. Besides, these supply
lines should answer to the following
conditions:
- Maximum water speed allowed in
the tubes.
- Moderate pressure in the tubes.
- Pressure relief in the tubes.
- Obstructions.
Filtration systems
An adequate filtration choice is based
upon the content of organic and inorganic
solids obtained through prior water
analysis. Filters are always placed finer
ones last, so the larger particles are the
first to be removed.
Every localized irrigation system must
ING. DANIEL
include a filter unit and a chemical water
treatment unit, since any obstruction in
t h e s y s t e m can r e s u l t in reduced
application uniformity, which in turn
decreases efficient water application.
Obstruction problems can be classified,
according the type, into physical, chemical
and biological.
The right filter system and accessories
consist in an appropriate choice of their
different elements based upon the features
of the emitter, water quality and the
operating conditions. The following are
some of the filters available:
1. Sand filters.
2. Centrifugal separation filters.
3. Net filters.
4. Ring filters.
Any option can be manually or automatically operated.
Design alternatives
There are different approaches to
design, depending upon the criteria
involved. For example, in a auto-balanced
emitter its necessary to maintain a 20%
pressure differential in order to obtain a
10% differential in expense; the idea is to
achieve a 95% uniformity.
Based upon this parameter, different
distributions can be applied in supply and
main tubes, as well as in cleaning lines
which end in drain valves (thus eliminating
the need for manual, line by line, draining ).
These cleaning lines can be placed at the
head or the inside of the plot, depending
upon:
- Cultivation work.
- Size of the plot and length of the row.
- Plot configuration.
- Cost of the equipment.
Once these aspects have been defined,
we can talk about different designs for a
localized irrigation project.
VELAZQUEZ
DUARTE
I. Main line, secondary line
with a pressure regulator
and non-balancing emitter
The basic construction of this system
consists in two parallel lines, joined by a
swing, harboring the pressure regulator.
In the field, its adequate for flat or
uniformly slanting plots, even steep ones,
since this system allows the plot to be
divided into small regulated sections, thus
reducing the impact of the slant.
II. Main line with a manual valve
to regulate incoming pressure
and a non-balancing emitter
This system eliminates several connections, and the regulators, which makes it
a price alternative for level plots. The
decision to design tubes where the
incoming pressure drop is controlled by
manual regulating valves (meeting specific
quality r e q u i r e m e n t s for chemical
application, resistance to handling and
continuous field operation), and loss of
friction caused by the diametrization of
the tubes, is only recommended for flat,
uniform or very moderately slanted fields.
The operation of this system requires
the person in charge of irrigation to
calibrate the valves with a gage by opening
and closing them, whatever the case, to
set designed work pressure at the entrance
of each plot.
III. Main line with a hydraulic
pressure regulating valve
and non-balancing emitter
The principal objective of this alternative is to facilitate operation and insure a
specific water volume applied to the crop,
cutting time and failures associated with
manual pressure calibration.
Design
alternatives
This design basically consists in supply
tubes, main tubes and regulating valves,
whose function is to keep a steady incoming
pressure in the plot according to hydraulic
design (notwithstandingpossible pressure
changes in the supply tubes), through a
regulating mechanism placed on the
outside of the valve. This mechanism
requires only one calibration to set a
definite and correct pressure in the plot.
For irrigation changes, the valves only
need be completely open or shut.
Another advantage is that these valves
can be used in the event complete
automatization of the irrigation system is
desired, since they allow the installation
of remote control (solenoid) units for multicable, mono-cable or radio control
equipments.
IV. Main line with a manual
or hydraulic valve and balancing
emitter
In plots with irregular or rough
topographies, the balancing emitter can
satisfy the need for efficient and uniform
water application.
Its hydraulic mechanism has caused
an impact on the development of different
production areas whose topography didn't
permit the use of non-balancing emitters
at a reasonable cost.
The uniformity of this system doesn't
depend upon regulating valves or tubes.
All emitters are balancing and capable of
providing the same nominal expense in
the field, regardless of their location.
The function of the valves is to merely
section; that is to open or interrupt the
flow into the field in operation.
Designs with a hydraulic valve (non
regulating) make future automatization
of the system possible.
Besides, with this kind of emitter,
30
systems
designs for level slanting plots are feasible,
since its possible to have longer watering
lines where cultivation practices allow it
and obtain up to 95% uniformity, with a
simpler design which saves on equipment
maintenance and operation.
The balancing emitter owes its benefits
to its even distribution, superior to any
other type of emitter, thanks to its pressure
compensation design. In some cases, this
is achieved by reducing the output hole,
and in others, through pressure differentials between the watering line and
the emitter. Both balancing emitters offer
distinct advantages.
System selection
Once the different and economically
feasible alternatives have been studied, a
final decision on the irrigation system will
also depend upon the producer's farming
criteria and practices.
Once the adequate choice has been
made (one which will meet all the
requirements of the crop ), its a good idea
to make an in-depth analysis of the
investment comparing the initial cost of
the irrigation equipment, against energy
consumption and operating expenses, since
these are directly interrelated. The lower
the pressure in the equipment, the higher
the initial investment and the lower the
permanent energy consumption. Keeping
this in mind, it's a good idea to design
guarding relationships between the
diameters of the lines and total dynamic
load of the pump to achieve an economical
balance for the producer.
An equally important aspect which
complements the choice of a system is the
purchase of accessories such as:
Acid and fertilizer injector, chemical
mixing t a n k s , e v a p o r i m e t e r and/or
atometer, tensiometers, humidity sensors,
ING. DANIEL
volumetric meter, automatic filter cleaning
systems, etcetera. These afford optimum
operation of the irrigation system and
thereby, the greatest benefits from this
technology.
An i m p o r t a n t factor in the final
selection are system operation and
maintenance considerations. These
shouldn't require specialized labor, where
there's none readily available. Besides all
the components making up the irrigation
system should be accesible and as near as
possible to the actual location of the
VELAZQUEZ
DUARTE
equipment.
Selection is a process to determine the
irrigation system to be used in an agricultural operation. Though the main criteria
is normally based on the cost ofthe different
alternatives, other factors can lead to a
choice which isn't the least expensive.
In general terms, the system should
satisfy maximum crop water and nutrient
requirements, with a uniformity equal to
or over 90%, where available labor can
handle and keep the system.
Design alternatives
and selection of localized irrigation systems
Bibliography
AQUAFIM.
Service Manual,
M . Micro-irrigation
Manual, 1990.
BOSWELL, J .
32
R . and A B R E U , H .
localizado, Spain, 1992.
LÓPEZ, J .
1994.
J. M.
Riego
Micro-irrigación,
1992.
Design
RANAHAN, Z . F E D R O .
Sap analysis
and fertigation
management
in horticulture with
plastic mulch
D R . HÉCTOR BURGUEÑO
B u r s a g , S. A. d e C. V.
DR.
O n e of the problems facing developing
countries is lack of food. This is due to
factors such as demographic growth and
poor distribution of natural resources,
water, climate and suitable farming land.
Mexico is not free of these conditions
and needs to increase its production.
Slightly over 50% of the Mexican
territory has a semi-arid to arid climate,
with scarce rains and saline soils. Its
necessary to improve irrigation and
fertilizing techniques, in order to increase
the availability of cultivable land by
increasing yields. This can be made
possible by adapting new methodologies;
it is therefore important for us to develop
the practice and utilization of mulch crops,
managed through conducted irrigation
systems and fertirrigation.
The combination of new agricultural
technologies also allows more efficient use
of raw materials, and at the same time
improves harvest quality.
Crop m a n a g e m e n t w i t h
new
a g r i c u l t u r a l technologies h a s been
implemented with the help of:
- Drip irrigation.
- Plastic mulch.
- Tensiometers.
- Soil solution extractors.
- Fertirrigation.
- Sap analysis.
HÉCTOR
BURGUEÑO
Mineral analysis of sap
from conductive tissue
I. Why analyze conductive tissue?
Plant analysis con be considered a
classical means to control fertilizing and
nutrition of the vegetables grown.
The most commonly used reference to
carry out this control is the leaf. Evidently
its generalization under the concept "foliar
diagnosis" arises from the fact that it's an
easily accesible part of the plant, and its
position or level in the plant is easy to
determine.
However it's not evident that this is the
best option. In effect, in the case of
vegetables which produce an important
biomass in a s h o r t period, foliar
composition varies slowly with respect to
the rate of growth of the plant. Leaves
aren't, therefore, a sensible enough
reference organ to evaluate the nutritional
status of these plants.
Quite the contrary, it's evident that
conductive tissue (stems, petioles, axillar
sprouts) permanent and directly related
to the "supply source" (radicular system)
and the "consumers" of the mineral
elements (leaves and fruits) constitute a
more apt indicator.
Inspired by the work carried out by
Sap analysis and fertigation
management
in horticulture
with plastic
Routchenko, more than ten years ago, Dr.
Philippe Morard, director of the Plant
Physiology Laboratory of the National
Agricultural School of Toulouse (ENSAT),
France, designed a quick and simple
method to follow plant nutrition through
sap analysis of the conductive tissue.
- Quick, since from an analytical point
a view, tests are made directly and without
preparing extracts from the conductive
tissue.
- Simple, because this method requires
axillary sprouts or petioles during the
entire cultivation cycle.
These analysis concentrate mostly on
the main kinds of chemicals present in
conductive tissue fluids:
N03-; NH4+; H2P04-; K+; Mg++; Ca++
Besides Na, Fe; Zn; Cu; Mn;
pH and electric conductivity of the sap.
According to Dr. Morard, the global
amount of an element present in the plant
fluids reflects its adsorption conditions,
while ionic fraction of a mineral element
constitutes a surplus or reserve from which
the plant supplies itself according to its
needs.
Sap analysis technique is b e t t e r
adapted to the follow-up of a rapidly
growing annual plant than foliar analysis.
II. Why carry out a regular follow-up
on plant nutrition?
Since this technique is important
because of its speed and sensitivity to
variations in nutritional flow, it also entails
36
mulch
new concepts on the interpretation of these
analysis.
In effect, it's a well known fact that the
flow and concentration of mineral elements
found in conductive tissue vary with
regards to several parameters, particularly:
- Insolation.
- Time of day.
- Age and developmental stage of the
plant.
- Temperature and relative humidity
of the environment.
Based upon the above, and as opposed
to foliar diagnosis, this technique makes it
impossible to refer to standard optimum
values; in other words, to vulgarize
"concentration parameters" for the mineral elements of plants.
T h i s m e t h o d , which h a s been
experimented and corroborated, consists
in continuous control of macro and
microelement concentrations during the
development cycle, and especially during
the production stage.
For example, in tomatoes of a specific
growth, 6 to 10 samples are taken between
the blooming of the first cluster to the end
of the harvest. These are quickly analyzed
(48 hours), and the results are recorded on
a graph. That allows us to follow the
evolution of each element analyzed in
function of the time, and so obtain a profile
of the nutritional status of each irrigation
plot.
Fertirrigation will not be practiced
based upon preestablished standards, but
according to the tendency in concentration
evolution of the two subsequent samplings.
DR. HÉCTOR
HIGH VALUES
•
BURGUEÑO
•
•WITHOUT INTERVENTION
U1
LOW VALUES
HIGH VALUES
•ELEMENT SUPPLY
LOW VALUES
HIGH VALUES
•DECREASE OF SUPPLY
LOW VALUES
In Europe, high and low value scales
were experimentally established. The low
value is the threshold of deficiency
(determined by a crop outside the ground
for every element); the high value is the
threshold of concentrations leading to
antagonism.
NO '
3
Grow stage
Fructification
stage
K
From the work done by doctors Morard
and Roucolle, we have o p t i m u m
concentration variation parameters for mineral elements regarding physiological
status of greenhouse cultivated tomato.
These are provided in the following table
only as an indicator. (Climate and
photoperiod conditions are different to
those prevailing in our country.)
+
NH
4
PO
4
H
2
++
++
Ca
Mg
Max.
3,300
4,400
180
320
150
170
Mean
Min.
2,000
800
3,900
3,400
110
50
200
130
80
20
110
60
Max.
2,900
4,400
100
200
90
170
Mean
Min.
2,000
1,100
3,800
3,500
80
50
180
130
45
20
120
80
management
in horticulture
On the other hand, during my doctorate
work in France (1985-1987), while working
with greenhouse tomato plants, we studied
the influence of different cultivation
systems on the mineral nutrition of the
plants, both in uncovered and mulched
soils, as well as in off-ground substrata
(volcanic rock, peat, expanded clay and
hydroponic). We found that in all the
treatments used, as long as acceptable
mineral nutrition is maintained, no
significant differences in mineral content
of the sap can be seen due to type of crop
or substratum. Fruit quality doesn't
depend upon the cultivation systems but
on adequate fertirrigation.
III. Importance of this method to
nutritional control in vegetable crops
For more than ten years, French horticultural producers control fertilization of
their crops, mainly tomato and cucumber,
aided by this method of permanent analysis of sap drawn from conductive tissue.
This methodology is being commercially
exploited in France by the Europe Sols,
S.A. company, which pays royalties to the
ENSAT Laboratory.
What does this n e w technique
provide growers?
Better control over mineral nutrition of
the plant.
Intensively managed crops (plastic
mulch, drip irrigation, fertirrigation,
greenhouses, etcetera) display a very
important capacity for biomass synthesis.
In full production, these plants can manufacture the equivalent of their own fresh
weight every two days. (The composition
of the leaf varies slowly with respect to the
rate of growth.)
Underthese conditions, permanentcontrol of a balanced mineral nutrition is
w<ith plastic
mulch
indispensable. An appropriate fertirrigation formula can, in effect, become unbalanced within a few days according to plant
needs. Such imbalances can result in:
- Reduced yield.
- Inferior product quality.
This is why its advisable to practice
sap analysis every 10 to 15 days from
initial blooming until full production.
IV. Sap analysis in Mexico
We've used this technology based upon
the following:
- Sap from plants of a given species,
placed under identical environmental
conditions, shows no a p p r e c i a b l e
differences in chemical composition.
-Changes
affecting
element
availability in the soil generally translate
into modifications in t h e chemical
composition of the sap. These modifications however, can be partially masked by
the intervention of other phenomena;
especially variations in growth rate and
by interaction produced at different levels.
- Among the ecological conditions,
intensity and duration of sunlight are
factors which can substantially modify,
activating or reducing plant metabolism,
hydric nutrition conditions contribute to
establish the chemical composition of the
sap characteristic to the mineral nutrition
of the plants. Sudden changes, especially
irrigations after a drought, also affect the
mineral nutrition of the plants; in most
cases, temporarily.
- High yields correspond to a certain
chemical status in the sap. However, a
given favorable composition will not
necessarily lead to high yields due to
possible depressing external factors.
- Sap and foliar analysis provide a
converging look at the plants' nutritional
status, but ultimately, the wide variation
in mineral elements present in the sap is
DR.
more important than the variation of these
elements in the leaf.
- When searching for the source of
anomalies, sap analysis provides a way to
discover them, when they're caused by
malnutrition.
- These methods are precise enough to
allow the nutritional status of a crop to be
classified as: insufficient, good or excessive.
V. Analytical process
and operating standards
Sampling should be carried out three
hours after dawn. We've done so from nine
to eleven at the most.
Sampled plants must be representative
of the maj ority of the population, especially
as far as development and color.
The number of organs per sample will
depend upon the plant species and the
juiciness of its conductive tissue. It
shouldn't be less that thirty.
The parts of the plant sampled are
axillar sprouts or petioles, depending upon
the species.
The position of the organ to be sampled
will be the fifth rank of growth after the
growth apex.
When sampling we carry along:
- an ice filled ice box,
- 250 cc glass jars with fight fitting
plastic lids,
- Anhydrous ethyl ether, and
- a permanent ink marker.
The samples are placed inside the jar
with a little bit of ether (30 to 50 cc) to stop
tissue metabolism. Afterwards they are
kept cold in the ice box up to two hours
maximum after the sampling has ended.
Samples are frozen in the lab to
completely stop their metabolism. The sap
is then extracted by pressure (squeezing),
and directly analyzed.
N0 3 " and H 2 P0 4 " analysis are done by
HÉCTOR
BURGVEÑO
colorimetry. Other elements are analyzed
with the atomic adsorption spectrophotometer.
Results are expressed in parts per
million (ppm).
During t h e 1993-1994 season in
Culiacán valley and the Ruiz Cortines
area in Sinaloa, we carried out numerous
foliar and sap analysis in crops such as
tomato, bell pepper, squash, cucumber
and melon. We were able to corroborate
the better indicative response of the true
nutritional status of the crops through the
variations in mineral element concentrations in the sap, whereas foliar analysis
showed no significant variations.
Out of the results from more than 500
sap analysis practiced in different irrigation plots during different stages of development, we present the following variations in mineral element concentrations
in the sap of tomato and bell pepper crops.
These concentrations are given in three
levels classified as:
Level 1: Mineral concentration of plants
showing optimum growth levels, with a
tendency towards higher concentrations
indicating excessive fertilizing.
Level 2: Mineral element concentration
of normally developing plants.
We estimate that optimum nutrient
concentrations in the sap, which culminate
in a crop exploiting a good share of its
genetic production capacity, are located
between the levels described above.
Level 3: Concentrations close to nutrient
deficiency, making a timely intervention
necessary.
It should be noted that the numbers
that follow do not represent the maximum
or minimum values detected, nor their
averages. These are mineral element
concentrations deemed sufficient to carry
out adequate crop nutrition management
through fertirrigation practices.
39
management
in horticulture
with plastic
mulch
Tomato sap analysis
Mineral element concentrations (ppm)
N, NO H PO
3 2
4
+
++
++
+
K
Ca
Mg
Na
Zn
Cu
Fe
Mn
pH
C.E.
Level 1
1,300
280
4,500
200
270
50
2
3
1.3
3
5.7
15
Level 2
1,000
200
3,600
80
200
30
1.2
1.6
1
2
5.6
14
Level 3
850
170
3,300
50
180
10
0.6
0.8
0.4
0.7
5.4
11
Bell pepper sap analysis
Mineral element concentrations (ppm)
N, NO H PO
3 2
4
+
++
++
+
K
Ca
Mg
Na
Zn
Cu
Fe
Mn
pH
C.E.
Level 1
1,700
280
7,660
80
700
70
3
5
2
6
5.6
21
Level 2
1,200
220
7,000
40
550
30
2.5
3
1.5
5
5.4
20.5
Level 3
900
160
6,500
30
400
18
1
1
0.5
2.5
5.3
19
We can briefly conclude that foliar
analysis report data about what already
h a p p e n e d to t h e crop, w h e r e a s a
n u t r i t i o n a l follow-up based upon
variations
in m i n e r a l
element
concentrations, indicate what's happening
at that moment.
Fertirrigation crop management is
based upon the application of fertilizers
with respect to crop density; nutrients
provided in grams per plant per day.
Its very important to know the initial
nutritional levels of the soil, as well as the
concentrations and types of salts present
in the irrigation water, since this will
enable us to make a good selection of the
chemical content of the fertilizers to be
40
used, and reduce the risk of having plugged
up drip holes. On the other hand, in the
m a j o r i t y of cases b a s e or bottom
fertilization can be avoided.
In fertirrigation, chemical balance
variations during the different vegetative
stages of the crop will be carried out
according to the nutritional needs of the
plant, supporting the results obtained
through sap analysis.
It should be kept in mind that in
intensive pseudohydroponic crops, the
immediate needs of plants are very
important.
Below are two tables showing examples
of seasonal fertirrigation programs for
tomato and bell pepper crops.
DR. HÉCTOR
BURGVEÑO
Bibliography
(1987). Influence de (liferents
systèmes de culture sur l'alimentation
hydrique et minerale de la tomate
(Lycopersicon esculentum Mill.). These
de docteur i n g e n i e u r . ENSAT,
Toulouse, France, 286 p.
MORARD,
Contrôle de
la nutrition et de la fertilisation des
cultures légumières par l'analyse de
sucs extraits des tissus conducteurs.
SETC. C. R. Acad. Agric. de France,
Octobre 1982.
ROUCOLLE,
BURGUENO, H .
MORARD, P . ETKERHOAS ( 1 9 8 2 ) .
P.
et
ROUCOLLE,
A.
(1983).
Diagnostic de la nutrition et contrôle de
la fertilisation de la tomate et du
concombre par l'analyse des sucs
extraits de "gourmands". PHM NFI 242,
pp. 37-41.
A. ( 1 9 8 2 ) . Projet de find 'études.
ENSAT. 181 p. + Annexes.
( 1 9 7 5 ) . Contrôle de la
nutrition minérale des plantes au moyen
de l'analyse des extraits frais de tissus
conducteurs. I N R A , Bordeaux, 1 4 3 p.
ROUTCHENKO, W .
41
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UREA SFT ABÖN
NH45G4
1
>.63
46
20.5
0
0
0
0
0
0
0Ï
OS
OX
OX
OX
OX
OX
OI
50 X
502
OX
01
01
OI
02
OX
OX
OX
OX
OX
CaNQ3 POLIFSF AC FOSF «IT POT
KNÖ3
H3P04
1
1.3?
1.6
1
«1.30
$3.00
»2.15
10.5
10
0
13
0
34
85
0
0
0
0
46
0
1?
0
0
OX
OX
OX
OX
OX
OI
OX
OX
OX
02
OX
OI
OI
OX
OXOX
OX
OX
OX
OX
100X
1001
100X
1001
1001
1001
1001
1001
1002
1001
OX
100X
¡OOX
1002
100X
702
701
50X
OX
OX
1
1
II
till
III u u
tut
VALLE DE CULIACAN, SIN.
7
CULT IVO: 0MATE DIVING
FECHA DE TRANSPLANTE : 20-25-1-93
USAR-)
NIT AH0N
N03NH4
1
$.62
33.5
0
0
0
N
ESUÎLISRIO
:
APL. ¡FERTIÓACION: KILOGRAMOS DE FERTILIZAWES/HECTAREA/DIA
p
K ..DIAS; ; g / o i i 3 3 . 5 - 0 - 0
46-0-0 20.5-0-0 10.5-0-0 10-34-0
0-85-0
:
1.00
1.00
1.00
i. 00
1.00
:. 00
1,00
i . 00
i.00
-. z
0.
1.50 .10;
1.30 .40,
:.¡0
.60!
.50 .80
.80 1.501
.70 1.60,
.70 2,501
.60
2.80 ;
.50 2.001
: •
.4,
5 t
20;
9¡ ;
UI
7,
22;
¡31
¡81 ¡
;
i
, Ï
1.4
1.4
;
I
I
!
i:6
i.3 Ì
1.1
3.11
4.79
5.83
6.03
5.00
5.97
5,57
5.05
3.01
3.12
3.06
3.50
3.37
3.15
3.26
2.68
2.39
2.15
1.42
¡.23
2. ¡9
2.27
3-0-46
0-0
.36
1.91
3.17
a. 02
6.50
7.94
7.10
2
2
5
9
6
127
¡UNIDADES FERTILIZ. Kg/Ha/
;
N
P2Û5
K20
i;
II
I!
i!
II
lì
l;
;1
1.04
1.65
2.20
2.43
3.46
2.85
2.90
2.61
2.02
2.09
2.60
2.97
2.56
2.67
2.77
2.25
2.03
1.83
1.21
1.04
1
2
4
5
6
5
4
TOTAL UNIDADES FERTILIZ.
12,343 PLANTAS POR HECT/
42
MATE
if
.8
50
0
0
0
96
. I ¡FERTI6ACIQN KILOGRAMS DE FERTILIZflKTES/HECTflREfl/PERÎODO
H I ! 33.5-0-0
46-0-0 20.5-0-0
5 5 - 0 - 0 10-34-0
0-86-0 ¡3-0-46
7!!
Ì4I!
li!
ss;:
2811
52; i
5!!
15! 1
8; i
15.55
67.03
46.63
120.55
72.01
65.72
39.02
111.05
39.16
56.12
28.52
40.87
632.85
(392
69.39
to
15.32
48.93
26.94
62.93
29.34
29.46
16.72
47.37
18.52
22.12
»0
»0
»0
d i ' UN IDA0E3 FEST I L I Z . Kq/Ha/PERIÖDO
ITI!
N
R205
K20
TOTAL
i ; Kg/fia/F
i5i•
'9ii
'4!i
¡711
«¡1
¡91 i
5U
8;!
Mi!
1;!
li
,!
¡:
Ü
I;
I;
.
11
;
Ü
0-
5.21
23.11
17.61
48.63
31.17
31.31
20.30
57.52
26.24
37.60
258.70
13.02
.00
41.59
2.31
22.90
7.05
53.49
29.18
24.94
24.94
25.04
46.94
¡ 4 . 2 1 36.55
40.27
143.80
¡5.74
73.47
¡8.80
75.20
270.01
439.45
317.65
«953
5.02
¡5.32
63.43
54.21
71.46
55.61
156.31
421.3c
»906
TOTAL
Kg/Ha/P
0-0-60
;
i
1
23.48;
18.271
¡19.84,
122.44;
¡25.34!
409.37
«287
30.5e
¡20.99
88.89
246.91
155.56
190.¡2
129.63
434.57
208.64
244,44
1,850.62
»2.536
¡8.23!i
67.01;,
47.56; !
131.30,
81.04;;
103.31;;
71.06;
241,5911
115.45,;
131.60; I
1.008.15
43
LA FERTIGACIOî»
tut
tut
un
Ut)
itti Itti tilt
V A L l E DE OlifiCM. SIN.
CULTIVO: E E L l FE-FE* VERDE.
FECHA DE TSANSFLANTE: 27-25-1-93
;
FECHA
¡DEL
AL
NÍT AHON
N03NH4
1
i.62
33.5
0
0
0
NÛHSRE:
FORHÚLA:
DENSIDAD:
PRECIO:
NITROSE«):
FOSFORO:
POTASIO:
AZUFRE:
1
2
3
4
5
Uli 6
7
e
9
0
USAR==>
litt
¡001
100Ï
10ÖZ
100!
100Z
100Z
¡OOZ
¡OOZ
100Í
¡OOZ
OREA SFT AHON AC NIT POLIFSF AC F0SF
NH4304
H3PÜ4
HNÛ3
1
1.3
1.39
1.6
1
$3.00
4O
20.5
55
0
10
0
0
0
34
85
0
0
0
0
0
0
0
0
0
0
OZ
OZ
0!
Oí
0Ï
¡II
OÏ
os
0Ï
Oí
oz
Oí
0!
OZ
OZ
OZ
oz
Oí
oz
oz
oz
oz
oz
oz
oz
oz
oz
oz
oz
oz
OZ
OÍ
OZ
oz
Oí
Oí
OÍ
0!
Oí
Oí
100Z
100Z
¡ooz
¡ooz
¡ooz
¡ooz
¡ooz
100Z
100Z
100Z
EQUILIBRIO
::EI'AD,: »FL. ;FERTI6ACI0K KIL06RAH05 DE FERTÍLIZAKTE / HECTAREA /
,1
?
K ; DIAS.! q/OL 33.5-0-0
16-0-0 20.5-0-0 55-0-0 10-34-0 0-85-0
i ¡30-K-ÍI
14-JI-93
! 2.5
0.
2, IÎS-JL-93 21-.Ü-93 , 1.00 2.00 .00!
r • ll-ñ-IZ T-«:-93 .
I.èO
30!
4 ,£-«11-93 23-ÍÜ-93, 1.00 1.00 .40!
..00 .80 .80,
5 ,:4-¡¡;L-=3 6-1-94
1/-I-94 , 1.00 .80 .90;
- ; ,7-1-94
7: -18-1-94
28-Ì-94 • ¡.00
.30 .sv;
,29-1-94
7-11-94 , ¡.00 .90 1.00!
i ä - i i - 9 4 . 1.00 .60 .80!
: i ,8-11-94
10-111-94, 1.00 .60 .60!
0 i; ¡ 9 - I ; - 9 4
,,
,.uii
7:;
lo,,
16,,
¡4!,
Ili!
tlü
10!!
:li¡
20.il
-!
• i. !
.3
.6 !
.4
.6 ¡
.7 ;
.6 i
.8 !
!
.3 !
3.30
5.50
¡0.20
7.39
9.10
9,96
3.25
4.33
7.03
3.28
3.71
4.21
9.55
¡2.12
8.87
6.25
2.92
5.01
2.36
1.48
¡31
UNIDADES FEST
N
P
1.11
1.84
3.73
2.79
3.94
4.48
4.13
4.73
3.35
2.10
TOTAL UNIDAI
32,757 PLANT
44
BELL PEPPER
IR FOT
KCL
AC SULF
H2S04
1
i.e
». 60
«.SO
0
0
0
0
60
0
0
96
0Ï
0Í
Ol
Ol
Ol
Ol
Ol
501
501
1001
1 TOTAL Í IFERTISftCION KILOGRAMOS DE FERTILIZANTES / HECTAREA / PERIODO.
; TOTAL
H l - 6 0 1 Kg/Ha/d! 1 33.5-0-0
44-0-0 20.5-0-0
55-0-0 10-34-0
0 - 8 5 - 0 13-0-4« 0 - 0 - 6 0 1 Í Kg/Ha/P
1
1
1
1
3.941
2.231
2.101
6.551 1
9,831
19.661 I
13.101
19.661
22.931
19.661
26.211
16.361
9.831
49.50
38,47
163.14
118.27
127.39
109.59
105.04
121,21
97.56
125.08
1,055.26
»654
48.78
30.32
112.41
52.55
51.90
46.34
32.10
50.07
26.01
29.58
»0
»0
ú / D I A ! K g / H a / d ! UNIDADES FERTILIZ. Kq/Ha/PERIODO
(20
! 1). FEST!
N
P205
K20
3.871
5.52;
10.82;
6.70!
19.241
12,08!
9.92Í
13.71!
8.04!
4.61!
16.58
12.89
59.72
44.67
55.14
49.23
45.47
47.29
36.85
41.50
41.46
25.78
95.55
44.67
44.11
39.39
27.26
42.56
22.11
25. I i
.00
.00
17.91
17.87
44.11
44.31
36.38
47.29
29.48
25.14
LIZ./HA./CICLO-
409.74
408.04
262.49
.001
.001
1.12!
1.12!
3.15!
4.03;
3.31;
4.731
2.65!
1.26;
iCTAREA
»0
»0
TOTAL !
Kg/Ha/P !
58.04;
38.66!
173.18;
107,211
143.37!
132.93;
109.131
137.13!
88.441
92.18!
1,080.27
480.05
»1,440
1
38.95
38.84
95.90
96.33
79.08
51.40
32.04
1
1
1
;
1
39.41; 1
24.571 ;
41.901 1
432.53 105.57
I93C
»64
98.28
68.80
314.50
205.66
275.1b
252.25
216.22
262.08
180.18
196.56
2,073.71
»3,086
Cultural vector
control of virus:
plant louse
and white fly
M . C . OCTAVIO POZO CAMPODÓNICO
Instituto Nacional de Investigaciones
Forestales y Agropecuarias
M.
Introduction
I n the past few years, viral disease has
become the most serious problem in
horticulture production in Mexico, since it
reduces yield and quality, principally in
solanaceous crops (peppers, tomatoes, etc.)
and cucurbitaceae (melon, cucumber,
squash, watermelon) with a range of
infection from 20 to 100%. Damage
depends upon the severity of the virus
involved, the phenological stage of the
crop, and the speed at which the epidemic
spreads.
These crops become infected with
several virus through various vectors. For
example, pepper crops have registered the
presence of (TEV) Tobacco Spot Virus,
Cucumber Mosaic Virus (CMV), Tobacco
Mosaic Virus (TMV), Tobacco Ring Spot
Virus (TRSV), Potato Y Virus (VYP), the
geminivirus complex which causes a
disease known as Pepper Yellow Curl
(RACH), and is also linked to Pepper Mild
Tigre Virus (PMTV), Serrano Golden Virus and Pepper Huasteco Virus (PHV).
Tomato crops have also registered the
d i s e a s e s m e n t i o n e d above,
and
additionally Tomato Bush Shrinking
(TBSV), Tomato P e r m a n e n t Disease
(EPT), Tomato Spotted Wilting (TSWV),
etc. 6 ' 10 ' 11
C. OCTAVIO
Pozo
CAMPODONICO
Vectors registered as transmitters of
one or several of these viruses are, in the
first place, aphids. Myzus persicae and
Aphis gossypii are outstandingly efficient
transmitters, followed by harvest flies,
trips, Paratrioza cockerelli, a psyllid, and
the now famous white fly, most efficiently
represented by Bemisia tabaci. Symptoms
caused by diseases transmitted by these
i n s e c t s a r e v a r i e d a n d have been
meticulously described for each crop.
However, in spite of the knowledge
generated by the identification of vectors,
their transmission methods, host range
and an understanding of the etiology and
epidemiology of the disease, problems have
become more severe since the consignment
of the first viral disease in 1971. By the
mid-eighties these problems had become
critical in some regions, while the virus
transmitted by the white fly appeared in
the early nineties, causing a 40 to 80%
damage among the 70 thousand ha of
peppers and tomatoes infected. 10
Viral transmission
On their own, viruses do not penetrate
their hosts. They do so through wounds
caused by m e c h a n i c a l d a m a g e to
developing root tissue inside the soil, or
due to leaves brushing against each other
CULTUMÎECTOIÔNTRO^^VINIS^LANHOUS^N^VHIT^
with the wind. This process is also carried
out very efficiently by another organism
which introduces viral particles from a
sick plant to a healthy one. These
organisms are called vectors, and are
generally insects, nematodes or fungus.
Many viruses are also transmitted through
seeds, pollen and parts of plants used in
vegetative propagation such as cuttings,
rhizomes, guides or stolons and bulbs. 7 ' 9
The virus as a parasite is only active
during the replication phase inside the
living cell. The result of this replication is
a great number of viral particles which are
stored in inactive state in several parts of
the cell. These become activated again
when transmitted to other plants, or other
parts of the plant. Under these circumstances, it is clear that virus survival
depends almost exclusively on the survival
and prosperity of its host. It is important
to differentiate, ecologically speaking,
these two transmission categories: viruses
dispersed independently from the plants
through a vector and those dispersed
through plant parts. The exact underst a n d i n g of these viral transmission
mechanisms, and latter development of
the disease are important to design future
prevention and control measures (9).
Virus vectors
In Mexico vectors with the greatest
economical significance are transmitted
by insects. The most notorious of which
are aphids and white flies that transmit
several kinds of viruses.
Aphids. More than 190 species of
disease-transmitting aphids have been
identified, but the most common are: Aphis,
Myzus, Brevicoryne,
Rephalosiphum,
Macrosiphum
and Toxoptera, which
altogether t r a n s m i t more t h a n 160
different viruses, most of which cause
50
mosaic and yellow symptoms. 7
Most aphids transmit non-persistent
type viruses. In this case, the insect
acquires the virus while feeding. The
virus isn't swallowed but carried in the
oral apparatus (probe) and retained only a
few hours. Inoculation also takes place in
a matter of hours (maybe a few seconds or
minutes). Non-persistent viruses can be
transmitted through the sap and have a
wide range of hosts. In Mexico nonpersistent viruses transmitted by aphids
are the Cucumber Mosaic Virus (CMV),
Tobacco Spot Virus (TEV) and Potato Y
Virus (PVY) among others, which can be
mechanically transmitted. 11
White fly (Bemisia tabaci). At present,
this is the most important and widely
distributed vector in the country. It
generally causes yellowing, foliar curling
and some mosaics. Initially, these viruses
and vectors probably could only be found
in tropical and subtropical areas, from
where they have since spread to other
ecological environments with a great
capacity to adapt and form new biotypes.
In general, the white fly transmits
v i r u s e s of t h e s e m i - p e r s i s t e n t and
persistent category. An acquisition period
of 24 to 48 hours is enough to render
viruses ineffective. The virus observes a
latent period inside the body of the insect
which lasts from four to twenty hours. It
can be acquired by the nymphs, persist
during pupation and be transmitted by
the newly emerged adult. 7
The virus is carried the insect's
hemolymph, which can be swept away by
the wind and thus transmitted over great
distances. White flies prefer to feed on
young tissue and on the right side of leaves.
They transmit the geminivirus complex
which causes the disease known as Pepper
Yellow Curl (RACH) formed by Tomato
Curl (CdTV) and Pepper Mild Tigre Virus
M.
(PMTV), Serrano Golden Virus (SGV) and
Pepper Huasteco Virus (PHV) which are
not mechanically transmitted. 11
Dispersal patterns
Distribution patterns for the disease in
the field provide valuable information to
identify the type of vector involved. For
example, if after the initial presence of the
disease, the infected area remains static
and doesn't spread, it means that the
virus is probably in the soil, in which case,
the vector would be a fungus or nematode.
On the other hand if initial presence of the
disease is in individual plants evenly
distributed within the field, the dispersal
C. OCTAVIO
Pozo
CAMPODONICO
agent is likely associated to be associated
to the seed.9
The primary stage of an epidemic
caused by aphid-transmitted viruses
mainly involves solitary plants which
invariably can be found on the edges or
borders of the plot. The disease progresses
inside the field through solitary plants
inoculated one by one from the areas first
infected.
A similar situation can be observed in
viruses transmitted by the white fly, except
for the initial infection period, which can
occur in the presence of groups of two or
three plants. Transmission to other plants
along the row can be expected according to
the period the fly retains the virus.
Table 1
Disease dispersal pattern and probable vector*
Dispersal pattern
Probable vector
Restrained, static initial infection,
infected plants are grouped.
The vector is in the soil: can be fungus of
nematodes.
Uniform distribution of isolated infected
plants.
Seed of acarus infection.
Isolated plants restricted to the edges of
the plot.
Aerial vector, possibly aphids.
Groups on infected plants and linear
dissemination.
Aerial vector, possibly white fly.
Secondary dissemination.
* Taken from Nelson, M. R. 1991.
Control of viral disease
Contrary to fungus and bacteria,
viruses can't be controlled with chemical
agents. There are c e r t a i n antiviral
compounds under development, but high
costs, high phytotoxicity and legal
considerations have impeded t h e i r
commercial use. Therefore indirect control measures, such as genetic resistance
and vector control represent the only
practical means to control the virus.
In the course of research on viral
disease, the greatest success has been
achieved in the understanding of the
structure and composition of virus. These
Cultural
vector control of virus: plant louse and white fly
studies were very well supported by the
most advanced technology such as the
electronic microscope, ultracentrifugal
units, spectrophotometers and electrop h o r e s i s t e c h n i q u e s , serology and
molecular biology methods. This knowledge served to lay down the framework
for a control strategy against viral disease,
and its main contribution has been
diagnosis processes in which its necessary
to correctly identify the problem viruses
and have a good understanding of their
epidemiology and ecology.9
A description of some of the most
common control methods follows.
A. Genetic resistance
Cultivars genetically resistant to
viruses and/or vectors represent the most
effective strategy to control viral disease,
since they keep viruses from penetrating
plant tissue or avoid their multiplication
and movement inside the plant. However,
since crops are infected by a virus complex
and possibly by many varieties with the
help of one or more vectors, it is extremely
difficult to obtain good results with
traditional genetic improvement methods.
Save for some relatively isolated cases,
success with this method has been very
poor. It can be said that improved
resistance to the vector is what should be
sought, since a genera or species like
aphids, and particularly Myzus persicae,
are responsible for the transmission of
several types of geminivirus. There is
hope t h a t biotechnology and current
development of transgenic plants will in
the future serve a practical application. 11
52
B. Cultural control
Even though cultural control of viral
disease is a very broad concept, as far as
we're concerned, it refers to integrated
vector management, including a series of
practices tending to minimize or avoid
vector activity inside the crop.
In the development of integrated control of viral disease, the greatest success
has been met by broad management or
control propositions such as production of
virus-free m a t e r i a l s (seeds, stolons,
cuttings, tubers, rhizomes, plants, etc.)
and the control of alternating hosts of the
virus and the vector.
Some experimentally proven practices,
validated by growers, are described
below. 8 ' 9
Plastic mulch
Both aphids and white flies are sensitive
to reflecting sunlight. This effect can be
achieved with reflecting tapes or plastic
mulch, which make it difficult for these
insects to approach the crop, and in the
case of vectors, decreases the incidence of
viral transmission.
Plastic mulches have been used for
other purposes: water use optimization,
weed control, temperature conservation,
etc. However, according to experimental
d a t a and t h e experiences of m a n y
producers and technicians, mulches offer
the lowest percentages of viral infection as
can be seen in Table 2, where plastic
mulch shows a clear advantage affording
good control u n d e r h i g h infection
conditions. 12
M.
C. OCTAVIO
POZO
CAMPODONICO
Table 2
Use of plastic mulch to control viral disease in pepper. INIFAP,
Percent of diseased plants
Weekly
sampling
4*
3*
2*
1*
13.10
0.00
0.00
1
0.02
59.58
5.20
12.50
2
17.29
16.16
72.10
23.54
31.25
3
36.00
86.60
31.20
39.50
4
92.90
100.00
89.50
90.20
5
1988*
5*
3.33
9.58
13.10
17.90
24.10
* 1. Black plastic. 2. White plastic. 3. Aluminum plastic. 4. Untreated witness. 5. Intensive chemical control.
** Taken from First International Congress on New Agricultural Technologies.
Manzanillo, Colima, Mexico, 1993.
On the other hand, while evaluating
the efficiency of black plastic mulch over
Myzus persicae population dynamics in
melon crops in southern Tamaulipas, and
the effect of the latter upon yield (Figure 1,
Table 3), it can be seen that aphid populations appeared in the mulched plot during
the sixth week after transplanting. Virosis
infection was noted on the seventh week,
and coincided with melon plants spreading
over the mulch, thus impeding its reflecting
action. In the unmulched witness plot and
the plot with chemical control only, plant
lice populations were detected during the
second week; disease set in during the
fourth week and registered 100% infection
by the ninth week.2
As far as production, the protection
afforded by plastic mulch is evident, since
export fruit yield was 300% greater than
that of the witness, and represented a
benefit-cost ratio of 1:2 according to existing prices and production costs at the time.
Table 3
Treatment
Mulched
Unmulched
Melon yielc (boxes/ha)
National
Export
515
330
174
116
Yellow traps
Over the past few years, the use of
yellow glue t r a p s has increased in
integrated virus management programs.
Other
298
154
Cultural
FIGURE 1. PERCENT OF V1ROSIS AND VECTOR POPULATIONS
IN TREATMENTS WITH AND WITHOUT PLASTIC MULCHES.
54
M.
The fact is that various insects, including
aphids and white flies, respond positively
to the action of the wave length reflecting
yellow (500-700 nm). This has been used
as a control measure against these insects
to decrease the propagation of viral disease
in horticulture crops.
Data from experiments carried out in
southern Tamaulipas (INIFAP) clearly
C. OCTAVIO
Pozo
CAMPODÓNICO
demonstrate t h e advantages of this
practice (Table 4). After 14 weeks of
observation, treatment with yellow traps
plus chemical control showed 19% of sick
plants; treatment with yellow traps only
registered 33.5% and the witness, 87.5%.
Likewise the number of adult white flies
captured by sampling was significantly
lower in the yellow trap plot.
Table 4
Effect of yellow traps on adult Bemisia tabaci.
Percentages of diseased plants and fruit yield.
CESTAM-INIFAP, 1988
Treatment
Yellow traps
+ chemical control
Yellow traps
Witness
% virosis
Average no.
of white flies
Yield
(two harvests)
kg/ha
19.0
3.2 a
3,062 a
33.5
87.5
3.5 a
6.3 b
2,879 a
535 b
On the other hand, while evaluating
yellow traps in contrast to chemical control, the former proved to be statistically
equal to the best insecticides (Table 5).
55
Cultural
Table 5
Effect of yellow traps and different insecticides on adult Bemisia tabaci.
CESTAM-INIFAP, 1989
Treatment
Permetrine
Lamdacialotrine
Cipermetrine
Yellows traps
Fosfamidon
Endosulfan
Witnesses
Average NQ
of white flies
Yield
kg/ha
2.3 ab
2.9 abc
3.5 abc
11,647 a
11,669 a
3.6 abc
3.8 be
3.8 be
4.7 c
Polypropylene cloth and plastic net
covers (floating covers, tunnels etc.). In
some areas of the country, crops are
covered with synthetic cloth to avoid
contact between plants and vims vectors.
This technology is rapidly spreading. In
Mexico, the first experimental evidence
was gathered by INIFAP-CNPH in melon
crops in t h e valley of Apatzingan,
Michoacán. At present there is more
experience in crop management with
plastic covers and several materials for
this purpose are available in the market.
Studies carried out by the Postgraduate
College in the states of Morelos and Sinaloa
in squash and tomato crops shed more
light on the advantages of this technique. 1
Likewise, in Yucatán where viral damage
to tomato crops was over 50% with more
than a 70% reduction in yield it was
possible to live economically with the
problem by developing an integrated
strategy for vector control which includes,
a m o n g o t h e r practices, p l a n t u l e
production in nurseries covered with
polypropylene cloth.4 And so, all over the
country covers in different modalities
56
10,768 a
7,346 a
9,165 a
8,438 a
3,632 b
(floating, micro-tunnels, sheds etc.) are in
relative use.
This technology, however, has great
disadvantages which limit its use in
different producing regions. Among these
is the short protection period, since most
crops must be uncovered when blooming
starts due to floral abscission generated
by adverse environmental conditions
inside the tunnel or floating cover. Another
disadvantage is excessive vegetative
development, principally in tropical
regions where the quality of solar radiation
is poor. Inside tunnels or floating covers
plants don't receive adequate light so their
vegetative development isn't normal: they
grow long internodes which make weak
stems. On the other hand, high temperatures and relative humidity inside the
structure afford an ideal environment for
fungus and bacteria infections.
Plastic screen barriers. One of new
alternatives to correct the disadvantages
of floating covers and tunnels described
above, so as to better benefit from the
comparative advantages they offer, is to
use antivirus or antivector screens as
M.
barriers around the crop. Synthetic
barriers measuring 2 m high minimize
insect access and serve as windbreakers
with the added advantage that normal
cultivation labor can be carried out in the
plot u n d e r n o r m a l e n v i r o n m e n t a l
conditions of light, t e m p e r a t u r e and
relative humidity.
According to e x p e r i m e n t a l obser-
C. OCTAVIO
POZO
CAMPODONICO
vations made in southern Tamaulipas by
INIFAPto determine population dynamics
of white flies through traps set at different
heights, it was found that between 60 and
70% of the population was captured at an
altitude of less than one meter; 85 to 92%
was caught between 1 and 1.5 m., while
only 8 to 14% were found above 2 m
(Table 6).
Table 6
Population dynamics of white flies at different altitudes.
INIFAP, 1994
Height of the traps
(cm)
% of white fly*
Height of the traps
(cm)
% of white fly**
70
33
30
32
100
29
60
25
150
24
90
14
200
14
120
12
150
9
200
8
* Data furnished by M. C. Joel Avila Valdez from six weeks of sampling carried out in 1987.
** Data gathered by the autor after six weeks of sampling in 1993.
With this information, plastic screen
barrier efficiency over white fly population
dynamics in serrano pepper crops was
evaluated. In a highly infected plot, a
300 m2 (30 x 10 m) area was isolated
with antivirus plastic screens. Every
day the population dynamics of the insect
were determined both inside and outside
the barrier through visor counts. Three
days before starting these counts, the
white fly population which remained inside
the barriers was controlled with Permetrine and Endosulfan. Results are
shown in Table 7, where the advantages of
synthetic barriers to control vectors are
evident.
Cultural
Table 7
Population dynamics of white fly inside and outside plastic barriers.
INIFAP, 1994
NQ of days
White fly population White fly population
on the outside*
in the inside*
Observation
Chemical control
1
3
86
2
4
82
2
5
8
0
6
12
0
7
32
1
11
127
2
12
133
6
13
137
10
14
110
9
19
197
46
20
199
61
21
126
4
22
8
1
North
North
Chemical control
North
* Ten visor strokes per sampling.
We have p r e s e n t e d h e r e some
experiences which may contribute to
minimize the effects of vector insects.
Unfortunately a successful solution to the
problem isn't easy and generally requires
multiple strategies. These must take into
account ecological conditions prevailing
in the region, an understanding of the
58
viruses involved in order of importance, a
good understanding of the epidemiology
and adequate knowledge of the biology
and ecology of the vectors. With all this
information, experts in integrated pest
management (IPM) can design a control
program adequate for each region.
M.
C. OCTAVIO
POZO
CAMPODONICO
Bibliography
1
2
3
AVILA, V . J . y Pozo, C. 0 . 1 9 9 1 . Establecimiento de una parcela de validación
para el control de enfermedades virales
en melón. Memorias IV Congreso Nacional SOMECH. Saltillo, Coahuila,
p. 204.
DÍAZ PLAZA, R . y RAMÍREZ CHOZA, J .
8
GREEN,
S.
K.
and
KIM, J .
S.
1991.
Characteristics and control of viruses
infecting peppers: a literature review.
AVRDC. Tech. Bull. N 2 18, 60 p.
GARZÓN, T . J . A . , BUJANOS, M . R . y BYERLY,
Presencia de
virus en los cultivos de chile Capsicum
annuum L.) y tomate (Lycopersicom
GARZÓN, T . J .
A.
1987.
M. R. 1991. Plant
virus
management. Trabajo presentado en el
diplomado "Administración y Eficiencia en la Producción de Hortalizas".
ITESM-Campus Querétaro.
9
NELSON,
10
Pozo, C. O. 1991. Estudio y control de
las enfermedades virales en el cultivo
de chile. Trabajo presentado en el
diplomado "Administración y Eficiencia en la Producción de Hortalizas".
ITESM-Campus Querétaro.
11
Pozo, C. O. 1993. Control de virosis en
el cultivo de chile. Minisimposio II. Manejo integrado de virosis en cultivos
hortícolas. V Congreso Nacional de
Horticultura. SOMECH-Veracruz.
12
Pozo, C. O. 1993. ler. Congreso Internacional de Nuevas Tecnologías Agrícolas. Manzanillo, Colima, México.
M. K. F. 1992. Manejo integrado de la
enfermedad "permanente" del tomate
(Lycopersicom lycopersicum L.) en el
Bajío. Informe de Investigación C A E B .
6
G R E E N , S . K . 1 9 9 1 . Guidelines
for
diagnostic work in plant
virology.
AVRDC. Technical Bulletin N2 15, 63
p., second edition.
L.
1991. Bioecología y control integrado
de la mosquita blanca Bemisia tabaci
Genn. (Homoptera: Aleyrodidae). Campo Experimental Zona Henequenera.
C I R S E - I N I F A P . Publicación Especial,
número 3.
5
7
AVILA, V . J . y WOLFENBARGER, D . A . 1 9 9 4 .
Yellow trap and insecticide for control
of white fly and virus incidence on
pepper. In press. J . Entomological
Sciences.
4
esculentum Mili) en México. Informe
de Investigación CAEB-INIFAP. Tomos de Virología II. Sociedad Mexicana de Fitopatología, pp. 156-18.
ACOSTA, L . P . , RODRÍGUEZ, M . R . y G u z -
MÁN, R. P. 1991. Epidemiología del chino del jitomate y su control mediante
cubiertas flotantes en Morelos. Memorias XVII Congreso Nacional de Fitopatología. Puebla, Puebla. México, 70.
Improvement and
control of indoor
horticulture
D R . J O S É LÓPEZ-GÀLVEZ
"Las P a l m e r i l l a s " E x p e r i m e n t a l S t a t i o n
DR.
Contents
1.
2.
2.1.
2.1.1.
2.1.3.
2.1.4.
2.2.
2.3.
2.3.1.
2.3.2.
3.
3.1.
3.2.
3.3.
3.4.
4.
4.1.
4.2.
4.2.1.
4.2.2.
5.
6.
Introduction
Greenhouse agriculture in Almería
The physical environment
Climate
Water
Soil
Transformation background
Present situation
Technical aspects
Economical aspects
Technological breakthroughs in Almeria-type greenhouses
Plastic materials for closures
Microclimate
Water management techniques in crops
Economical results
Micro-climate improvement in low-cost greenhouses
Techniques for temperature improvement
Techniques for radiation improvement
Closure materials
Orientation and shape of the cover
Conclusion
Bibliography
JOSÉ
LÚPEZ-GÁLVEZ
DR. JOSÉ
1. Introduction
T h e concept of a g r i c u l t u r e h a s
traditionally been understood to pertain
to activities strongly dependent upon the
natural physical environment. It's not
surprising, therefore, that the agricultural
prosperity of a place was conceived as
something related to favorable soil, climate
and water conditions. Any unfavorable
circumstance with regards to any of these
factors would limit farming potential to a
degree that could result in its losing all
economical interest.
The aforementioned limitations can be
helped through various technological
innovations. This is the case of crops
growing on artificially created media.
Thus, the development ofhydroponic crops
and crops growing on substratum makes
it necessary to re-evaluate the traditional
role of the soil. On the other hand, the use
of greenhouses also modifies environmental variables totally or partially. It's
reasonable to assume that, under such
controlled growing conditions, the limiting
factor would be water; but in this respect
also, notable achievements have been
made during the past thirty years with
localized irrigation systems. All these
important transformations have been
made possible, to a great extent, with the
LÛPEZ-GALVBZ
appearance of plastic materials.
It's hard to imagine our modern day
world without plastics. The general value
of this idea (as can readily be seen in the
generalized use of plastics for manufacturing all those things that make our lives
easier) can be faithfully applied in the
area of agriculture, which has thus
benefited from a true revolution. These
m a t e r i a l s not only improve w a t e r
management (with distribution networks,
regulating deposits, irrigation systems and
drainage networks) but also allow us to
alter climate conditions in the environment
with mulches, small tunnels, protection
screens and even greenhouse roofs.
Mexican agriculture is no exception to
the use of plastics to optimize irrigation
water consumption and to control or alter
climate (Reyes, 1992). The use of passive
climate g r e e n h o u s e s allows tomato
production during the months of May and
June (transplanted in January) in the
state of Coahuila (Ibarra and Quesada,
1992). Borrego and Co. (1992) show how
the nopalito (Opuntia ficusindica) is
produced in greenhouses with satisfactory
economical returns in areas near the border
with the United States. Experiences with
greenhouses in different parts of Mexico
promise better productivity, which makes
greenhouses all the more interesting
Improvement and control of indoor
horticulture
within the framework brought about by
t h e N o r t h A m e r i c a n Free T r a d e
Agreement, NAFTA, signed by this
country, Canada and the United States.
These new circumstances undoubtedly
reinforce the competitiveness of Mexican
agriculture, through the adequate use of
its advanta-geous climate to obtain firstrate crops, and even expand its productive
calendar.
One of the greatest examples in
intensive in-doors production techniques,
with respect to European competitive
terms, is in Almería. I assume that the
experience brought about by its "sandy"
cultivation system, proper to the Almería
coast, as well as research done on the
subject under passive climate greenhouses,
makes it possible to draw particularly
useful knowledge for the development of
agriculture in other areas with moderate
temperatures. These local technologies
have brought together artificial soil
preparation, localized irrigation and the
establishment of simple greenhouses, with
low investment costs. These create a favorable micro-climate which can increase
yield and crop precocity, which make them
competitive against more sophisticated
and expensive greenhouse techniques
developed elsewhere.
I wish to reflect on the potential of
greenhouses referenced in moderate
climate areas. I'll describe Almería
66
techniques used to improve natural
environmental conditions. I'll try to give
some orientation on the design of the
buildings used. In short, the idea is to
share an experience which can prove useful
under Mexico's agroclimatic conditions,
which are better than those of its partners
in NAFTA.
2. Greenhouse agriculture in Almería
2.1. The physical environment
The province of Almería lies in
southeastern Spain. 90% of its greenhouses
are concentrated in an area west of the
capital city. This area limits to the north
with the Gador Sierra and to the south,
with the Mediterranean; it's located
between 36941' and 36s49' latitude North
and 2S33' and 2S54' longitude West. Since
its inception around 1965, greenhouse
cropping has grown significantly inside
this strip of coast.
2.1.1. Climate
This information, from the 1982/1983
to 1991/1992 campaigns, was taken from
the 155 m high automatic meteorological
installation of the "Las Palmerillas"
Experimental Station, located on 36a48'
l a t i t u d e North, and 2 e 43' longitude
West.
DR. JOSÉ
LÓPEZ-GÀLVEZ
Air temperature
Minimum absolute temperatures are
over (FC. January and February are the
coldest months. Maximum absolute
temperatures are over 309C during the
months between June and November.
O
N
F
M
A
M
MONTH
MAX.
M. 24h
M . DAY
ABS. MIN.
ABS. MAX.
MIN.
M.
NIGHT
Relative humidity
KM.
Minimum humidity values under 20%
are common. Practically every month of
the year includes days with values under
30%. Each month there are moments close
to saturation.
O
N
D
—e—
J
F
M
A
M
MONTH
•—
1
MAX.
M . 24h
M . DAY
ABS. MIN.
ABS. MAX.
MIN.
J
J
A
S
—«—
M . NIGHT
67
Improvement
and control
oj
Evaporation
Evaporation in a class "A" tank was:
Campaign
1982-1983 to 1991-1992
Yearly average
mm / day
5,1
Yearly average
mm 1 day
17,0
Yearly total
mm
1.894,3
Wind
W i n d s a r e p r e d o m i n a n t l y westsouthwest and from the East. Breezes are
more frequent during summer nights.
Maximum gust was 112 km/h, blowing
120s Southwest.
MONTH
MAX. GUST
24 h. GUST
DAY GUST
K\Ml/m2 DAY
NIGHT GUST
Global solar radiation
Mean monthly values are lower than 5
kWh/m2. day through the months of
November-J anuary.
MONTH
68
DR.
JOSÉ
LÚPEZ-GÁLVEZ
Rain
Scarce; annual average is lower than 250 mm.
Campaigns
1976-77 to 1990-1991
Greatest drought
84-85
Total
rainfall
(mm)
226,2
Máx. rainfall
in a day
(mm)
51,7
NBof rainy
days
(mm)
47,1
109,2
13,8
42,0
2.1.2. Water
Poor rainfall and high superficial
permeability of the soil don't allow
continuous waterways of relevance.
Subterranean waters are the most used.
There are three water deposits in the
area, and their contents, though of different
qualities, are considered acceptable for
present agricultural activities.
2.1.3. Soil
The soil of the area is very heterogeneous. In general, though, its basic (saline
and alkaline) soil, shallow and almost sterile.
2.2. Transformation background
The physical description of the area
gives it a certain desert quality. Historically, farming practices were seriously
difficult and rather impossible given these
extremely hostile edaphoclimatic characteristics, poor soils and extremely scant and
irregular rainfall, in addition to scarce
superficial water resources, strong and
frequent winds, all of which didn't make
adequate development viable.
Technological innovations have made
it possible to farm in this area, by changing
old limitations into new advantages. These
i n n o v a t i o n s w e r e geared t o w a r d s
alleviating the main limiting factors (soil
and water) and to get the most from the
beneficial factors. Thus, relatively benign
temperatures during the winter months
and excellent insolation translate into
improved crop precocity and productivity.
Drainage systems are unnecessary given
soil permeability. Even the winds have
become a positive factor, since they
eliminate the need for mechanical means
of ventilation and the cost associated with
the energy they consume, making greenhouse ventilation easy.
The clue to technological advancement
lies in advantageously relating water control (through irrigation) to soil control
(with sandy soil) and environmental control (with plastic "arbor-type" greenhouses). The resulting system can be
summed u p as irrigation agriculture
developed upon sandy soil, in low-cost
greenhouses not equipped with heating.
This whole body of applied techniques is
deemed "exportable technology".
and control o)
2.3. Present situation
growing (which is traditional in the area)
made with wooden and wire. The framework is fixed on wood poles set upon concrete blocks. Wire is used to anchor the
structure, tie the posts and form top and
side screens. These support the closure
material, which is flexible polyethylene,
placed between two wire screens, then
joined with short pieces of wire. Since
roofs are usually flat or with only a slight
inclination, they must be perforated to
eliminate rain puddles.
In the beginning, the greenhouses
described above were lower than 2 m; now
they can be higher than 2.5 m. This makes
it easier to grow crops of indeterminate
height, through training practices. All this
results in a functional greenhouse which
allows partial control of the microclimate,
reduces évapotranspiration (ET) in the
crop, curbs wind damage and slightly
improves the thermal regime.
2.3.1. Technical aspects
The irrigation system used isn't the
most outstanding feature of the cropping
technology being described. Even though
drip irrigation systems are the most
common, flood irrigation is still applied in
almost a third of the land irrigated. What's
truly characteristic are the soil preparation
techniques and the type of greenhouse
utilized.
The sand preparation technique was
implemented in the fifties. It includes
initial plowing and leveling, as well as the
addition of a 20 cm layer of vegetable soil,
mixed with 5 kg/m2 of manure. Another 2
cm layer of manure is applied next, which
is then covered with a 10 cm layer of beach
sand. All together, this makes four clearly
distinct strata, both in their physical as
well as their chemical structures. Their
positive effects last two to five years, after
which it becomes advisable to redo the soil
by hoisting the sand layer to replace the
manure.
In the sixties, the sand cropping technique was augmented with greenhouse
protection. A characteristic of these greenhouses is their simple, low-cost construction inspired by structures used in vine-
2.3.2. Economical aspects
The application of the above mentioned
techniques, adapted to the conditions of
the area, has enabled the implementation
of a very intense agriculture, one of the
most profitable in Spain. The following
table illustrates the spread of greenhouses
throughout the province of Almería.
HECTARES
26000
20000
160CO
1
10000
1
1 1
6000
0
i i i i i Mi i i i l l iHiflm
1965
70
68
71
76
79
81
i
83
86
i
90
DR. JOSÉ
The economical importance of this
agriculture, with regards to its share
in the gross domestic product (GDP) and
Sectors
Agriculture
(Greenhouse)
Industry
Construction
Servicios
Total GDP
LÓPEZ-GÁLVEZ
the demographical dynamics of Almeria
has been highlighted by Naredo & Co.
(1993).
1991 GDP by sectors
GDP (%)
Almería
18,7
(12,7)
Spain
11,1
13,7
24,3
8,8
62,9
56,6
100,0
4,0
-
100,0
Source: BBV. National income and its distribution by provinces, 1991, and own data.
The table shows how agriculture is
much more important to the Almeria
economy than to that of the whole of Spain.
This is more on account of the dynamism
of t h e region's a g r i c u l t u r e t h a n of
stagnation in other sectors. When we add
t h e goods a n d services r e l a t e d to
greenhouse cropping, we find that the
latter represents close to 70% of total
agrarian production and accounts for more
than 35 % of provincial GDP.
When we compare t h e d i f f e r e n t
territories, it can be seen that population
growth between 1965 and 1991 was
uneven. Coastal territories close to modern
intensive agriculture and tourism showed
substantial population growth. The rest,
which includes traditional a g r a r i a n
exploitations, showes decreased population.
71
and control of indoor
horticulture
Demographic dynamics of farming territories
in the Almería province
Population
Territory
Variation
1965
1991
124,1
192,2
54,9
Alto Almanzora
58,9
49,2
-16,5
Alto Andarax
24,7
16,1
-34,8
Bajo Almanzora
45,9
47,4
3,3
Campo de Dalias
64,7
117,0
80,8
Campo de Tabernas
21,3
12,2
-42,7
Los Vêlez
19,2
12,4
-35,4
Río Nacimiento
17,3
9,0
-48.0
376,1
455,5
21,1
C. de Níjar y B. Andarax
Total province
1991/65
Source: INE. Compiled by Research Studies of the Chamber of Commerce of Almería.
3. Technological breakthroughs
in Almeria-type greenhouses
3.1. Plastic materials for closures
The system is only viable when there
are contrasted quality plastics available
atareasonable price. Jorge &Bretones (1990)
describe the problems and the evolution of
closure materials. Among the first (in the
early seventies) major drawbacks of
plastics, they point out the following:
- Uneven film thickness.
- Rapid aging and degradation.
- Poor mechanical resistance.
- Poor thermal protection under low
temperatures.
These authors add that the improvement and evolution of plastics was carried
out efficiently, thanks to interdisciplinary
cooperation between the industry and
agrarian experimental centers. This resulted in long-lasting, thermal-insulating
films in the marketplace.
3.2. Microclimate
Greenhouse production results from
the improved environments these structures afford plants, in terms of light,
temperature, relative humidity and air
composition. The main objective of industrial greenhouses is to bring optimum
climate parameters closer to each plant
species. Research carried out to date on
the microclimate generated by the Almeria
greenhouse, enables us to pinpoint the
d i f f e r e n c e s b e t w e e n t h i s cropping
technique and the one used in said industrial greenhouses.
Given its lack of complicated means to
modify its microclimate, temperatures and
relative humidity in the Almeria-type
g r e e n h o u s e a r e below a n d above,
respectively, those prevailing outdoors
during a good part of the night (LôpezGâlvez & Co., 1991). However, since the
heat generated by the sun is better utili-
DR.
zed during the day, this greenhouse
improves the temperature integral and
shortens the period between the various
phenological stages, thereby increasing
crop precocity.
Consequently, it should be noted that
this crop system does not really fit the
usual concepts of "greenhouse cropping"
or "forced cropping"; nor do its installations
act like true greenhouses, and crops are
not "forced" with the introduction of strict
environmental controls. In fact, this system
focuses more on enhancing favorable natural conditions through simple and low
cost materials, than on creating an artificial habitat apart from the natural hostile
conditions.
The main feature of the Almeria-type
greenhouse worth mentioning however, is
its low cost and easy construction, which
doesn't require any specially trained labor. The fact that with an investment
(purchase and preparation of the land,
forming the sand bed, placing irrigation
system and buildingthe greenhouse) lower
than 20$/m2, this system achieves high
yields from various crops, over 5$/m2,
during an ample calender, only highlights
its economical advantages, even though
the microclimate it provides is far from
the optimum required by the different
garden vegetables presently grown under
these conditions (Montero & Col. 1984;
Lopez-Galvez & Bretones, 1988; LopezGal vez, 1991).
This is well illustrated by the fact that
during the years 1976-1984, average minimum temperature inside these greenhouses in January was 9.92C, and average
maximum temperature in July was over
37aC. These readings are pretty far from
what is considered optimum for many for
the crops under exploitation.
JOSÉ
LÚPEZ-GÁLVEZ
3.3. Water management
techniques in crops
One of the principal objectives of the
Almería irrigation system is to increase
water consumption efficiency. Here
irrigation management should focus on
obtainingthe highest possible productions,
avoiding hydric s t r e s s which could
diminish yield or quality. This is especially
important due to the scant capability of
the soil to retain water, which explains
the need to create an artificial soil (sand
bed), build regulating deposits (which have
spread throughout the crops) and implement drip irrigation systems.
Drip irrigation allows the application
of water and fertilizers with just the right
frequency and on the base of the plant.
Under this premise, the role of regulating
water and nutrients reserve traditionally
supplied by the soil are no longer essential
and serves as mere support to the crop. In
such a framework the only information
necessary for good water management is
knowing t h e c o n s u m p t i o n due to
evapotranspiration (ET) and that pertaining to salt washing. This data, together
with a knowledge of the yield of water
application by evaluating the irrigation
system, enables us to make reasonable
decisions regarding the amount of water
to be applied to the crop.
Best water management in the Almería
agrarian system has been based on the
following:
Estimate of the evapotranspiration of
the principal crops. It is known that during
previous experimentation, the precise dose
of irrigation -Castilla & Co. (1986) and
López-Gálvez & Co. (1990)- determined
ET consumption of the crops using
drainage lysimeters to obtain all the
components of the hydric balance:
Improvement and control of indoor
horticulture
ETc = R - L + AW
With the following variables:
ETc = évapotranspiration of the crop.
R = w a t e r supplied by rain and
irrigation. In our case, rain is nil.
L = lixiviated water
AW = variation of the water content of
the soil. Under the conditions of the AW30
tests.
For further experimentation there is a
class "A" evaporimeter tank, normalized
by the W.S. Weather Bureau. This tank
was placed inside a greenhouse growing
g r a s s (Lopez-Gâlvez & Co. 1988).
Considering that evapotraspiration of the
crop is measured by the expression [ETc =
k Eo], where Eo is the evaporation in the
tank and k is an adimensional coefficient
encompassing the tank and crop coefficient
-estimated [k = Etc/Eo]-, with data from
several years of tank evaporation, it has
been possible to write a series of index
cards giving required water dosages for
the different crops in periods of two weeks.
Evaluation of irrigation systems and
homologizing in the quality of the drip
branches. This evaluation and homologizing is to confirm whether the irrigation
systems are operating correctly. That is,
whether they're applying and adequate
amount of water on the crop occupied
surface and if this amount is uniform. Due
to potential risk of plugged-up drip holes,
drip irrigation systems have to be evaluated frequently. A part of good water
management is to check the system
periodically.
Caja Rural de Almeria ( 1985) promotes
work on evaluation of the drip irrigation
systems installed in greenhouse crops.
Final conclusions and recommendations
on work already carried out are the
following:
1. The quality of the installations is
acceptable. In general, the work done by
74
the companies in charge ofthe installations
is positive. However, there are certain
deficiencies in technical design which
reflect upon the cost of the installations.
These deficiencies could be easily corrected
by adapting the power of the pump, filter
and fertirrigation equipment to the true
needs of the installations.
2. Uneven water application, taking
into consideration that the systems under
evaluation were recently installed. The
basic reason for poor uniformity is deficient
drip holes, a fundamental factor the
installer should be considering.
3. Its alarming that almost 50% of the
tubes evaluated were not manufactured
with the right raw material. The quality is
unacceptable both by the UNE 53367
standard and international tube standards.
4. The need for more precision in the
diameters of the branches m u s t be
stressed, in order to avoid value disparity
and p r e f e r e n t i a l l y a d h e r e to those
expressed in present standards.
5. Once installed, the system is operated
without any sort of technical instructions
as far as water volume or fertilizers to be
used.
These results showed the need for a
guarantee document between farmers and
drip irritation installers, in order to overcome the deficiencies stated. Additionally,
a series of index cards was prepared
providing the steps to be followed while
evaluating irrigation systems. This was
done by adapting the method proposed by
FAO. These cards, together with average
water consumption in the crops, contributed to the following:
A. Drip irrigation systems. The degree
of quality in the tubes has improved. A
good part of the material used is made by
a quality manufacturer. Also acceptable
in most exploitations is the uniformity
coefficient in the application of water
DR.
through the irrigation systems. (Losada &
Co., research under way.)
B. Water expense. Has been reduced
from more than 7,000 m 3 /ha per year,
accordingto measurements taken in 1982,
to less than 5.500 m 3 /ha per year. Data
pertains to areas irrigated with good
quality w a t e r (López-Gálvez & Co.,
investigation under way.)
An adequate water management program should consider other factors such as:
Salt control. The distribution of salts
in the profile of drip irrigated soil basically
depends upon physical characteristics,
(texture and structure, for example)
besides other extrinsic circumstances, like
emitter expense, application frequency,
washing fraction and radical distribution.
Total wash is particularly hard to achieve
when using localized irrigation systems.
At Almería, the technique consists in
applying flood irrigation (30 to 40 mm) at
the end of the campaign. No soil salinity
problems of importance have surfaced,
even when irrigating with water whose
electrical conductivity is over 3 dS/m.
However, in our opinion, orientation to
the growers should be based upon more
detailed experimentation on the movement
patterns of water and salts in the soil.
Fertilizer management. The possibility
of applying fertilizers through the drip
irrigation system has implicit potential
advantages. Among these, a more precise
and efficient application, since it is done
JOSÉ
LÓPEZ-GÁLVEZ
by parts and directed to a specific place,
which reduces losses through filtration
and denitrification. The fertilizer management program should conform to the
water management program. It's advisable
to make frequent applications, trying to
cover the needs of the crop. In this field,
there have been many investigations
carried out in Almería (Castilla 1986;
Martínez, 1987; López-Gálvez, 1991.)
3.4. Economical results
This section summarizes representative economical data coming from the
i n f o r m a t i o n g a t h e r e d by t h e "Las
Palmerillas" Experimental Station
through a network of cooperating farms,
as well as through its own experimental
growing experiments. The data is from
the 1990-1991 campaign. All monetary
numbers in this document are given in US
dollars, at the average exchange rate
prevalent during the 1990-1991 campaign
(100 pta = $1).
Immobilized, fixed. Here we contemplate the purchase of the land, making the
sand bed, building the greenhouse, the
irrigation network and construction. Total investment was between 14 and 22
$/m2.
Productions and income. The following
table shows the values surrounding the
yields, prices and income for crops and
most common alternatives.
75
Improvement
Annual
alternative
1
horticulture
Production and ncome from the crops
Production
Prices
Crops
kg/m2
$/kg
Dutch cucumber
7-10
0,30-1,40
0,50-1,50
Kidney bean (vine)
3-6
2
Squash
Melon
3-4
4-6
0,40-1,60
0,25-2,00
3
Short pepper
Watermelon
3-4
5-8
0,60-3,60
0,15-1,20
Long pepper
Kidney bean (low growing)
Eggplant
Tomato
5-7
3-6
5-7
6-8
0,40-2,80
1,00-3,00
0,50-2,60
0,35-1,50
Year average
4
5
6
7
Normal expenses. Are between 2.20 and
3.70 $/m2 distributed as follows:
- E x p e n s e s directly related to crops
such as water, seed, fertilizers and phytosanitary products represent 30% of total
expenses. The resulting number compared
to that of other cropping systems is
moderately low, due to more efficient water
and fertilizer use. For example, with this
system (using the recommended dosage of
water) its possible to obtain 44 kg of
cucumber per m3 of water applied in the
fall-winter cycle. In monetary terms, this
represents more than $2.5 per m3 of water.
- Labor expenses represent 40% of total expenses, and vary quite a bit
depending upon the labor demand of the
different crops. It should be pointed out
here, that in one of the farms under study,
labor done by f a m i l y doubles t h e
productivity of paid labor. (Lopez-Galvez
& Co., research under way).
- Other expenses are shared between
replacing the plastic on the greenhouse
76
Income
$/m2
3,50-5,50
2,50-4,00
6,00-9,50
2,50-4,00
1,00-4,00
3,50-8,00
3,00-5,00
1,00-3,50
4,00-8,50
3,50-6,00
3,50-7,50
3,50-7,00
3,50-7,00
3,93-7,64
(usually every two years), changing the
manure layer in the sand bed (every three
to five years), and interests on circulating
capital.
Considering these data, internal yield
rate for the 1990-1991 campaign varied
between 10.4% and 18.1%. The average
for the whole Spanish agrarian sector
during the same period was 1.8%.
4. Micro-climate improvement
in low-cost greenhouses
This section examines several ideas
we've been working on at the "Las
Palmerillas" Experimental Station to
improve microclimate conditions and
increase crop productivity.
As everybody knows, in order to obtain
maximum productive potential, every
species and variety should enjoy adequate
light, temperature, humidity and carbon
dioxide parameters. The object of passive
greenhouses is to obtain prime products,
DR.
induce harvest precocity and broaden
production calendars. These installations
afford higher temperatures during the cold
months, which are not optimum for the
crop growth potential, but nevertheless
result in satisfactory quality harvests
which, in turn, are usually well remunerated. From the climate point of view,
the main negative aspects of these
greenhouses are:
- High temperatures in the summer
and low temperatures in the winter.
- High relative humidity percentages,
a n d c o n s e q u e n t l y , p r o l i f e r a t i o n of
cryptogamic disease.
- Lower incident radiation on the crops
than on the outside.
- Lower C0 2 concentration.
C e r t a i n techniques facilitate the
development of favorable environmental
conditions inside passive climate greenhouses. Their application should consider
that the different climate parameters
depend upon one another. If we modify the
ventilation, we'll be changing the temperature, relative humidity and air composition. Therefore, before modifying any
parameter we must analyze its effect on
the others.
To begin with, the future greenhouse
requires proper light and hence, an
adequate location. Its best to choose plots
that are exposed to sunlight all day,
avoiding low parts of valleys, ravines and
areas close to buildings or vegetation which
might project shadows on the land. Also,
its a good idea to keep away from valleys
where cold air is difficult to evacuate, or
places where fog, air pollution or other
factors inhibit solar radiation.
4.1. Techniques for
temperature improvement
Temperature can be increased using
JOSÉ
LÓPEZ-GALVEZ
thermo-isolating closure material. This
type of material usually contains products
with a low permeability to long infrared
radiation (between 7 to 14 pm) which, as
we know, is heat. The Spanish standard
states t h a t a material is considered
thermo-isolating when its transmissibility,
between said wave longitudes, does not
exceed 20%. There are flexible polyethylenes, EVA copolymers and PVC in the
market which meet these characteristics.
In Almería greenhouses its common
practice to place a second, temporary,
ceiling in the inside of the greenhouse to
improve temperature conditions during
the cold months, and the first phases of
development of the crop. In this case, the
material to be used should be thermoisolating, very transparent and thin, since
it doesn't require great mechanical resistance.
The high temperatures reached during
the day, especially during the summer
months, can be reduced using shades. This
technique should be applied very carefully,
since it's common to see shades in the
inside of the greenhouse, which doesn't
avoid heat penetration. That's why the
shades should be placed on the outside,
over the closure material, to shut out
radiation. Shade screens are made of
polypropylene fiber, which offers different
degrees of sunlight, depending on the thickness of the fibers. This thickness determines the percentage of desired radiation.
Another common technique to control
high temperatures, consists in whitewashing the roof of the greenhouse or
painting with any other (white or colored)
material that reflects part of the radiation.
Its important to use an easily washable
material that can be eliminated once the
hot season is over.
Experience at the "Las Palmerillas"
Experimental Station has shown that a
larger and well placed ventilation surface
77
Improvement
horticulture
(side and top windows), used wisely can
improve temperature, relative humidity
and carbon dioxide concentration inside
greenhouses.
4.2. Techniques for
radiation improvement
Any installation whose purpose is to
regulate climate variables, basically a
greenhouse, should try to minimize the
negative impact of climate at a reasonable
cost. Old constructions (using the right
materials, orientation and design) resulted
in acceptable environments. Modern
constructions base their climates on active
systems providing "environmental conditioning" by way of substantial energy
consumption.
In a passive climate greenhouse, the
objective is to collect prime yields with
regards to outdoors harvests. To that end,
sowing or planting should be carried out
during seasons when climate limitations
don't allow outdoor crops. Passive climate
greenhouses are intended to receive the
greatest amount of solar energy during
the months in which it is the most limiting
factor for adequate development. Radiation conditions in these greenhouses can
be improved during the winter months
with a good selection of:
4.2.1. Closure materials
A common feature of plastic materials
78
used in low-cost greenhouses is their
flexibility.
The most f r e q u e n t are:
polyethylene (PE), polyvinyl chloride
(PVC) and ethylene vinyl acetate (EVA).
The degree to which these materials
transmit solar radiation depends upon
their properties and thickness. A good
choice should take into account:
- The electrical static in some materials
causes suspended dust to stick, which
reduces transmissibility. This is especially
important in dusty areas where rain is
scant. Experiments carried out at "Las
Palmerillas" Experimental Station have
shown that washing greenhouse roofs
during the winter months increases their
transmissibility between 10 and 13%.
- Condensation produced on the inside
of the closure m a t e r i a l can reduce
transmissibility. Toneatti (1989) reports
a gain of up to 15% using anti-fogging
materials. To use them, however, the
structures of the greenhouses have to be
adapted. This type of material may have a
promising future once its present limitations are overcome, since it would help
reduce cryptogamic disease.
The following table shows transmissibility values to photosynthetically active radiation (PAR) for two materials (antifogging EVA a n d PE) placed on a
symmetrical slanting roof greenhouse (8fi
angle), with an east-west axis. Measurements were taken in the southern part of
the greenhouse (López Hernández & Co.,
1993.)
DR.
89
90
JOSE
LOPEZ-GALVEZ
|
91
MONTH / YEAR
4.2.2. Orientation and shape
of the cover
Orientation
As long as there exist no other limiting
factors such as the slant of the land or the
direction of dominating winds, the axis of
the greenhouse should be oriented eastwest or north-south, depending upon the
type of greenhouse (mono or multi-hooded)
and the shape of the roof. Although there
is no consensus among researchers on this
point, its generally standard that multihooded greenhouses are north-south
oriented to avoid shadows between the
hoods, except for asymmetrically roofed
greenhouses, where the shadow effect can
be eliminated. Crop alignment will always
be north-south.
Shape of the roof: when designing a
roof for a greenhouse, its important to
consider:
- Sun rays fall on the earth at an angle
determined by the latitude, time of the
year and day.
- Maximum radiation is obtained when
sun rays hit at a 90a angle.
These premises make it possible to
determine the angle that better maximizes
relative conditions in a greenhouse in any
given place and time. So, for the Tropic of
Cancer (23.5s) at solar noon, on December
21 or 22 (winter solstice), sun rays fall on
the Earth at a 43 s angle. Therefore, if we
wish to capture the most energy, we must
give our roof a 47 s angle on its southern
face, which supposes orienting the greenhouse, east-west, with the following
problems to consider:
- One is the size of the plot since the
span of sun rays, inside the greenhouse,
Improvement
horticulture
limits its width, unless we want areas
with different radiation intensities. A
study of an Almería greenhouse (36s 49'
latitude north), with an east-west orientation, asymmetrical (8 fi slant)22m wide
roof, found areas with different radiation
intensity along the north-south axis,
during the winter months. This clearly
affected harvest precocity and, thereby its
productivity (López-Gálvez, 1991).
This problem can be solved by adopting
an asymmetrical roof, with a larger face
exposed to the sun. The surface and slant
of such a face will determine the dimension
of the greenhouse regarding its northsouth axis. This can be increased with a
certain roof angle, by increasing the surface
of the sun-exposed face, or by building
several fixed hoods. In the latter case,
shadows between the hoods are to be
avoided. This limits the width of each
hood, since the sun rays penetrating the
hood are to fall on part of the surface
occupied by the next hood. Besides
care must be taken that part of the sun
rays penetrating on one side don't exit
through the other. To avoid this, we must
give the side of the roof opposite the sun,
a slant equal to or smaller than the
incidence angle of the sun rays. (In the
case of greenhouses located on the tropic
of Can-cer, this angle should be smaller
than 43s.
80
- Another problem pertaining to greenhouses with a slant over 20 s on their larger
faces is higher ceilings and, consequentially, costlier structures, besides more
operational difficulties (changing closure
material, placing shades, etcetera.
In sum, it is the technical-economical
aspects which decide the size and slants of
the asymmetrical greenhouse roof.
Research carried out at the "Las Palmerillas" Experimental Station has found
why these roof geometries (asymmetrical),
with angles around 10fi on the sun-exposed
face and 202 on the opposite face, have
improved radiation conditions, t h u s
increasing greenhouse productivity with
respect to the traditional flat roofed, and
symmetrical north-south axis greenhouses. (Lopez-G&lvez & Co., 1993.)
5. Conclusion
Its possible to improve productivity in
passive climate greenhouses. To that end,
its necessary to: choose the right closure
materials to improve thermal conditions,
augmenting them with double covers;
regulate temperature, relative humidity
and carbon dioxide concentration by
increasing ventilation surface with side
and top windows; increase the intensity of
radiation by guarding the orientation and
shape of the roof.
DR. JOSÉ
LÚPEZ-GÁLVEZ
6. Bibliography
BORREGO, F ; BRETÓN, J . A . ; MURILLO, M A .
G., 1 9 9 2 . Forzado en invernaderos de plástico para la producción intensiva de una hortaliza mexicana de alta demanda en Estados Unidos. XII Congreso Internacional de Plásticos en Agricultura, Granada. B - 1 3 9 .
M.y
FLORES,
LÓPEZ-GÁLVEZ,
F.
J.;
PÉREZ, J . ;
; CASTILLA, N .
BRETONES,
y ELIAS, F .
1988:
Comparación de medidas de evaporación en tanque evaporímetrico clase "A"
dentro de invernadero.
Justificación
del entorno de hierba (césped). VII Jornadas Técnicas sobre Riegos. Madrid.
B-12.
Caja Rural de Almería. 1985. Evaluación
de instalaciones de riego localizado financiadas por Caja Rural de Almería.
278 pp.
N. 1986. Contribución al estudio
de los cultivos enarenados en Almería:
necesidades hídricas y extracción de
nutrientes de cultivo de tomate de crecimiento indeterminado en abrigo de
polietileno. Tesis doctoral. Universidad Politécnica de Madrid. Caja Rural
de Almería. 195 pp.
CASTILLA,
CASTILLA, N . ; MONTERO J . I . ; BRETONES, F . ;
JIMÉNEZ, M . ; G U T I É R R E Z ,
E . ; MARTÍNEZ,
A. y FERRERES, E. 1986. Necesidades de
riego en los invernaderos de Almería. II
Simposio sobre "El agua en Andalucía". Universidad de Granada. Vol. I:
1992.
Res-
puesta al acolchado en el desarrollo
y rendimiento del cultivo de tomate
en invernadero, túnel y cielo abierto.
XII Congreso Internacional de Plásticos en Agricultura. Granada. E-19.
r a (2): 5 9 4 - 5 9 9 .
LÓPEZ-GÁLVEZ, J . ; GALLEGO, A . ; BRETONES,
F. 1990. Necesidades de riego de berenjena cultivada sobre suelo enarenado bajo
abrigo plástico. Mérida, Badajoz. B-3.
Productividad de
la judía verde en enarenada bajo invernadero en Almería. Tesis doctoral.
FIAPA. 225 pp.
LÓPEZ-GÁLVEZ, J . , 1 9 9 1 .
y BRETONES, F. 1 9 9 2 . Comportamiento climático del invernadero
tipo
Almería en los meses de invierno y
de verano. II Congreso Internacional
de Plásticos en Agricultura. Granada.
B-154.
LÓPEZ-GÁLVEZ, J . ;
y BRETONES, F . 1 9 9 0 . Colaboración interdisciplinaria. Clave del éxito
para el desarrollo de la plasticultura.
XI Congreso Internacional de Plásticos
en Agricultura. Nueva Delhi, India.
Actas, p. 1 . 1 7 - 1 . 2 8 .
JORGE, G .
Con-
sideraciones de tipo climático del cultivo de pepino holandés en los invernaderos de Almería. III Congreso SECH.
Tenerife-España. Actas de Horticultu-
LÓPEZ-GÁLVEZ, J . ; LÓPEZ HERNÁNDEZ, J . C .
91-102.
IBARRA, L . y QUEZADA, M . R .
LÓPEZ-GÁLVEZ, J . y BRETONES, F . 1 9 8 8 .
NAREDO, J.
SÁNCHEZ CARREÑO,
J.;
M.y CASTILLA, N . 1993."Análisis técnico-económico de estructuras
alternativas al invernadero de cubierta
plana parral-Almería.
Investigación
Agraria: Producción y Protección Vegetal. Vol. 8 (3).
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horticulture
L Ó P E Z - H E R N Á N D E Z , J . C . ; LÓPEZ-GÁLVEZ, J . y
Comparación de dos
materiales de cubierta para invernadero: uno de polietileno termoaislante y
otro un copolímero EVA con efecto
antigoteo. II Congreso Ibérico de Ciencias Hortícolas. Abril, 1993. Vol. II:
ARROYO, F . 1 9 9 3 .
1223-1227.
A., 1 9 8 7 . Comportamiento del
riego bajo enarenado en invernadero.
Balance de salinidad y fertilizantes, en
especial de cultivos depimientoy judía.
Tesis doctoral. Caja Rural de Almería.
230 pp.
MARTÍNEZ,
MONTERO, J .
I . ; CASTILLA, N . ;
GUTIÉRREZ,
y B R E T O N E S , F . 1 9 8 4 . Climate
under plástic in the Almería area.
E.
82
Working Party on Greenhouse Construction and Covering
Materials.
Karlsruhe, RFA.
NAREDO, J . M . ; LÓPEZ-GÁLVEZ, J . y MOLINA,
J. 1993. "La gestión de agua para regadío: el caso de Almería". El Boletín.
Ministerio de Agricultura, Pesca y Alimentación. Noviembre 1993. Número
9, p p .
15-22.
1 9 9 2 . La agroplasticultura en México. XII Congreso Internacional de Plásticos en Agricultura.
Granada.
REYES MONTIEL, H . ,
"Anti-fog Films: Facts
and Fiction". Plasticulture N2 8 4 . 1 9 8 9 /
TONEATTI, P „ 1 9 9 2 .
4: 6-18.
Corn plasticulture
in France
ING. L E D U J E A N
Centre National D u Machinisme
Agricole d u Genie Rural
D e s E a u s et d e s F o r e t s
ING.
LE DU
JEAN
Contents
Plasticulture
Why corn plasticulture?
Corn plasticulture in France
Climate
Soil
Varieties
Sowing and mulching machines
Plastic films
Studies of various factors relative to plasticulture in France
Solar radiation energy
Soil temperatures under plastic mulch
Water in the soil
The disadvantages of corn plasticulture
Advantages of corn plasticulture
Economical aspects
Conclusion
85
ING.
Plasticulture
I ^ l a s t i c u l t u r e refers to the group of crops
planted under or through a plastic mulch.
There is:
- A horticultural plasticulture which
utilizes tunnel greenhouses and plastic
mulch to produce garden vegetables and
flowers.
- A field plasticulture developed for
certain crops such as melon, lettuce,
grapes, strawberries, corn, etcetera.
Corn plasticulture is practiced with
clear plastic film, permeable to ultraviolet
and short infrared rays (solar radiation).
This clear film, however, partially seals
out (approximately 50%) long infrared
rays, emitted at night by the soil and the
plant.
Placing a clear plastic mulch between
the soil and the atmosphere produces
several effects; t h e m a i n one is a
greenhouse effect. During the day (short
infrared) sun rays warm the soil. At night,
approximately 50% of the long infrared
rays emitted by the soil and plant are
sealed in by the mulch, thus partially
avoiding a loss of heat in the soil and
temperature changes harmful to the plant.
This greenhouse effect allows heat to
accumulate in the soil.
Other effects are:
LE DU
JEAN
- Less evaporation. Evaporation is
considerably decreased by the mulch. Vapor arising from the soil condenses on the
inside of the mulch, returning to the soil.
When the plant emerges, it enjoys a longer
period of good humidity and heat.
- Better utilization of fertilizers, which
no longer leach; and better phytosanitary
product performance.
- Soil protection. This is very important
for lime soils, since phenomena such as
battance are avoided, and at the same
time soil structure is maintained. Erosion
phenomena (wind and rain) can also be
reduced when the plastic strips are
adequately placed on the soil.
Photodegradable low density polyethylene (LDPE) or thin (12 to 15 pm)
biomechanodegradable polyvinyl chloride
(PVC) are the plastics that serve as mulch
in corn plasticulture.
For your information, it takes two 45
kg rolls of 12 pm LDPE to cover one hectare
of corn.
Why corn plasticulture?
Plasticulture makes it possible to grow
corn in temperature limited areas without
too much risk to the crop. It's used on
lands which don't heat well in the spring,
on battant soils, and on clay soils which
87
Corn plasticulture
in France
can delay the planting date. It's also used
in areas which are humid in the fall or
where there's a risk of frost before the crop
reaches maturity.
In these "limit zones" plasticulture
enables producers to advance the planting
date, harvest drier grains, advance maturity date, introduce slower varieties and
obtain higher grain or whole plant yield
for storage in silos.
This illustrates how corn plasticulture
is a special technique applicable to particular areas.
In effect, in France, corn plasticulture
is only applied in certain northern and
western regions of the country, simply
because to the south of these regions
climate conditions (sunlight, temperature,
etcetera) allow normal corn cultivation,
without mulch. However, in countries
north of France, lack of sunlight and risk
of frost impede plasticulture.
Soil types vary a lot in the limit zones
where plasticulture is practiced. The
climates in each of these regions also differ
one from another, so it's necessary to
consider varieties, planting dates and
climate variations (in France 1989 through
1991 were years of drought, which was
very harsh on spring crops.)
Corn plasticulture is also applied in
other regions to help solve very specific
problems. For example, in Alsace, plasticulture makes it possible to harvest sweet
corn at different intervals, so the plant
industrializing the corn can double its
work schedule.
Corn plasticulture in France
N O R D ^ ^ ^ ^ ^ P ^
^ P A S DE CALAIS
NORMANDIE \
PAYS DE LOIRE
In France, corn plasticulture first
appeared in 1970. In the years that
followed, and until 1979, this technology
was tested and studied. During this period,
photodegradable plastics as well as
mulching and planting machines were
placed in the market. In 1983, in the
colder areas of Britanny, 5,000 ha of corn
88
BRETAGNE
ft
f
were planted under mulch. Corn plasticulture continued spreading until 1987. Then,
due to good climate conditions and cases of
plastic photodegradability, B r i t a n n y
showed a drop in acreage planted under
mulch. The subsequent drought years,
however, triggered the reinstatement of
this technique in the province.
ING.
NUMERO
HECTAREAS
30000-r
LE DU
JEAN
C O R N PLASTICULTURE USE IN BRITANNY FROM 1981 TO 1991
25000 - -
20000--
15000 - -
10000--
5000--
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
YEAR
At the same time, in the rest of France,
mulched surfaces continued to grow also.
Total in France for 1986 is estimated at
32,000 hectares, and for the 1991, the
number is 70,000 hectares.
Plasticulture is practiced in Aquitaine,
Midi-Pyrénées and Alsace, but it is mainly
in the regions from La Loire to Britanny,
Normandy and northern Picardy where
the greatest extensions are dedicated to
corn plasticulture.
Surface of corn grown under mulch in Britanny in 1991
Mulch cultivated corn in Britanny in 1991
Armor Coasts
16,000
Finistere
6,000
Morbihan
4,000
lile et Vilaine
3,500
89
Corn plasticulture
in France
Mulch cultived corn he•ctares
(AGPM estimate
1990
1986
1989
1,300
3,000
Northern Picardy
6,400
1,500
5,500
2,000
Total in France
32,000
La Loire
Normandy
1991
5,500
8,700
9,500
14,500
4,500
3,000
65,000
to 70,000
45,000
Source: Carpentier, 1992.
Corn plasticulture is especially applied
in the coasts of Armor, representing 11%
of total land dedicated to corn in that
department.
Total for France in 1992 is estimated at
70,000 hectares, but in 1993 we witnessed
a 30% drop in mulched surfaces, so total
surface for 1993 should be the same as
that achieved in 1990, in other words,
40,000 hectares. This decrease didn't arise
from climate conditions nor any other
t e c h n i c a l factors, but because of
uncertainty brought about by PAC and
GATT, talks which prompted growers to
postpone investments and reduce costs.
RGURE
16.
SUM
OF
SPRING
90
MEAN
(1951
TEMPERATURES O V E R
-
1975)
4=C
Climate
Corn plasticulture allows improved
conditions when the corn cultivation
process begins, so a satisfactory level of
yield and quality can be anticipated.
Plasticulture is applied in regions where
cool spring temperatures limit corn production.
The following two maps show limit
zones for corn cultivation, where the sum
of temperatures is between 1400SC and
1500 2 C/year (western and n o r t h e r n
France).
MAP
40.
"GRAIN"
CORN
SPRING
PLANTING
(1951
-
DATE
1975)
ING. LE DU
Tests carried out by AGPM*, ITC**,
INFRA*** and the National Meteorological Institute show that the best external
measure related to corn evolution the
grower himself can obtain, is the sum of
temperatures over a 6SC limit, approximately (below this temperature, the
plant is in a stage of retarded growth).
This criteria makes it possible to obtain
the best forecasts of blooming and harvest
dates.
JEAN
Between sowing and female blooming,
temperature needs are closely related to
the precocity of the hybrid. The later the
variety, the greater its need of heat to
reach blooming. Differences between
hybrids essentially arise from the fact
that they don't produce the same amount
of leaves: earlier varieties only produce
13, while later ones produce up to 19;
hence, differing blooming dates (Table 1).
Table 1
Sum of temperatuires (degrees) necessary for hybrids of different precocity
to achieve ilooming; number of leaves observed at blooming
Sum of
Number of
Varieties
mean temperatures
leaves at blooming
Bovee LGI
7702
13 to 14 leaves
s
Ema
770
15 to 16 leaves
s
Brulouis Inra 180
785
15 to 16 leaves
s
Liza
825
15 to 16 leaves
Oca
850s
16 to 17 leaves
s
Brio Grow 42
930
18 to 19 leaves
s
Eva
960
17 to 18 leaves
s
Autan LG 22
980
18 to 19 leaves
s
Concorde Pau 560
1,030
19 to 20 leaves
s
Ferax
1,075
19 to 20 leaves
Sources: AGPM-ITCF.
Studies on the evolution of water
content in the grain, show that for the
blooming-maturity period, water content
is closely related to the sum of temper a t u r e s received by the plant since
* AGPM: General Corn Producers' Association.
** ITCF: Technical Institute of Cereal and Fodder.
* * *INRA: National Institute of Agronomic Research.
feminine blooming. When these aren't limit
temperatures, maximum grain weight is
obtained with a 32% water content
(Table 2).
Corn plasticulture
in France
Table 2
Sum of temperatures (degrees) necessary to pass from blooming to stages
38, 35 and 32% of grain water content for hybrids of different precocities
Sums of mean temperatures at stages
Test years
Varieties
35%
32%
38%
Bovee LGI
Ema (1)
Brulouis Inra 180
Liza
Dea
Brio Asgrow 42
Eva
Autan LG 22 (1)
Concorde Pau 560
Ferax (1)
1979 to 1982
1984 to 1986
1982 to 1985
7352
795 s
7552
7402
820 s
8002
1980 to
1981 to
1977 to
1983 to
1984 to
7602
7902
775fi
8052
825 e
8352
820 s
825 s
850 s
835 s
860 s
880 s
890 s
875 s
1985
1986
1983
1986
1986
1980 to 1984
1984 to 1986
870 s
895 s
930 s
890 s
925 s
935 e
960 e
940e
Sources: AGPM-ITCF.
(1) Provisional results.
With these data it was possible to
establish a corn cartography, scaled to
France, taking into account climatological
risks. The sum of temperatures separates
the date of the first frost of autumn (see
the following map).
The g r e e n h o u s e
plasticulture heats the
months. This increase
sum between 1202 and
MAY 3
MAXIMUM
TEMPERATURE
18 9 C
MINIMUM
TEMPERATURE
10 s C
M E A N TEMPERATURE
18_t_lQ 1 4 2 C
2
EFFECTIVE TEMPERATURE
Ü
14 - 6 E 3
MAXIMUM
TEMPERATURE
•34 g C
MINIMUM
TEMPERATURE
• 16 2 C
C
JULY 30
UMIT MEAN TEMPERATURE
30_M6 2 3 2
c
EFFECTIVE TEMPERATURE
23 - 6 E 3 3 c
92
865 e
895 s
effect due to
soil for about two
corresponds to a
150s on base 6.
ING. LE DU
JEAN
Calculation of effective temperatures for corn
Each day, effective temperature is the average temperature under cover,
over the 62C level.
Effective temperature = Maximum temperature + minimum temperature _ g„
2
For a maximum of 18SC and a minimum of 102C:
- average temp, is 14s C
- available temp is 82C
Whenever necessary, two correction factors have been considered: when mean
temperature is under 6 e C, effective temperature equals 0.
When maximum temperature is over 302C, this value is limited to account for
stress.
For a given period, the sum of effective temperatures for corn corresponds to the
sum of daily average temperatures over 62C.
Soil
Soils are very different even in the
same limit temperature areas. They range
from the granite soils of Britanny to the
calcareous e a r t h of N o r m a n d y and
northern Picardy, with all the variables
these two soil types entail. (In the following
map, granite soils with an acid pH can be
found in the west, while calcareous soils
with a neutral or basic pH are located in
the central and eastern regions of the
northern part of France.)
93
Corn plasticulture
in France
Varieties
Varieties used in northern and western
France (in 1993):
- Northern Picardy-Normandy: DEA,
DK250, Fanion, Nobilis
- Ille et Vilaine-Armor coasts: DEA.
DK250, Nobilis, LG2250
- La Loire: Barbara, Corsaires, DEA,
DK250, DK300, Fanion, LG2310, Nobilis.
Some new varieties have given good
results, for example:
- Armor coasts: Anjou 207, DK 232
- La Loire: Anjou 305, Bilboa, etcetera.
The potential of any variety is related
to its precocity with later rates. Limits are
reached quickly (maturity, increased
drying costs.)
In agroindustry, grain hardness; in
PRECOOIY
other words the type (corne and corne
dente) are fundamental to the starch and
flour industries.
Criteria determining varieties destined
for animal feed (whole plant for storage in
silos or moist grain) are dry weight
production per hectare, flavor quality and
DMO (digestability of the organic matter
of the fodder).
Depending upon the variety selected,
planting density must also be determined
so the corn can fully develop its potential.
For example on the Armor coast, the
most used varieties are DEA and LG2250,
with a precocity rate between 250 and
300. For mulch-grown corn, slower and
therefore more productive (90,000, 105
plant^/Ha), hybrids are used (+50 precocity
index).
DENSITY BY PRECOCITY
POPULATION / HA
70,000
80.000
90,000
100,000
110«»
120,000
VERY PRECOCIOUS
PRECOCIOUS
SEMI-PRECOCIOUS
SEMI-PRECOCIOUS
SEMI-LATE
LATE
VERY LATE
BEDS, PRODUCT QUAUTV « D ECONOMICAL OPI1MUM SHOULD BE CONSIDERED
BEFORE SELECTING THE DENSI7V FOR A DETERMINED PRECOCilY RATE.
SOURCE: A3PM - I1CF
94
ING. LE DU
: 0.15 m
0,75 m.
0,15 m
WIDTH OF THE FILM: 1.35 m.
A
0.25 m ^ 0.25 m ^
—
•
0.25 m • 0.25 rn
*
W
*
^m
m
WIDTH OF THE FILM: 0.64 m.
SOURCE: JEAN71L
Certain equipment can be added on to
the machines:
- microgranulators (insecticides)
- systems to avoid grain waste, etcetera.
T h e s e m a c h i n e s are, t h e r e f o r e ,
very specific, and since their appearance in t h e m a r k e t in 1976, technical innovations have been directed
towards reducing their weight. This
enabled the use of less powerful, lighter
tractors, which in t u r n reduced soil
compression.
Sowing under mulch is a delicate
operation. It requires an experienced
driver and reduced speed: 1.5 b/ha.
We e s t i m a t e t h a t a sowing and
mulching machine can plant between 100
and 150 hectares per year.
Quality sowing requires t h a t the
plastic film be well buried in the ground
so it doesn't fly off. Also, perforations
much be sufficiently spaced (15 to
25 cm) to limit the action of the wind. This
JEAN
Sowing and mulching machines
These machines carry out several
operations:
- prepare beds
- place and fix mulch on soil covering
edges and row ends with soil.
- perforate the mulch with a spine
wheel.
- place one or several grains in the
holes made by the spines (possible depth
adjustment).
Machines are capable of sowing two or
four rows in single step and are adjusted
to the widths of the plastic strips being
used. (Plastic film strips measuring 1.35
m or 0.64 m.)
Sowing is carried out as follows (see
sketch).
involves multiple sowing, i.e. one or several
seeds per hole, in order to obtain desired
density.
Certain users prefer narrow strips (0.64
cm) to limit the action of the wind.
Plastics films
Films used in corn plasticulture require
good mechanical resistance to avoid any
tears during installation. This also implies
very good soil preparation before mulching
it (eliminating stones and clods). Film
should remain in its place six to seven
weeks (greenhouse effect) after which it
should autodestruct so it doesn't get in the
way of subsequent crops.
At present, in France we use two kinds
of films.
- P h o t o d e g r a d a b l e low d e n s i t y
polyethylene (LDPE) films.
- Biomechanodegradable polyvinyl
chloride (PVC) films.
95
Corn plasticulture
in France
Plastic LDPE-based films
Low density polyethylene comes from a
petroleum by-product called NAFTA. The
resin base of the film is made of this
polymer to which an absorbing agent (a
coordination compound made of iron,
cobalt, nickel or manganese) is added,
making it photodegradable.
The first films used, made of LDPE
resins were 30 pm thick and practically
weren't photodegradable. Later, linear
LDPE film (with a different linear
structure) was introduced, and its higher
mechanical resistance allowed thinner
films. Since 1981, 15 pm films have been
on the market, and in 1984 12 pm films
were introduced.
In France today there are at least four
different processes to manufacture these
plastic films. In c e r t a i n processes
industrials introduce a compound or mix
of polyethylene resins (linear, radical) and
photodegradable agents. By extrusion, this
compound is transformed into agricultural
mulch film. Certain manufacturers don't
use a compound, and carry out the
extrusion process by mixing polyethylene
and an additive in continuum.
According to our data, there are seven
extruders in France whose LDPE film is
produced for agricultural use.
LDPE based film rolls, sold for corn
plasticulture, are 1.35 m wide, 3,100 m
long and are used for mulching two rows of
corn. A roll weighs about 45 kg, and
represents a film surface of 4,185 m2.
Approximately 930 m2 are buried (15 cm
on each side) so one hectare of corn requires
two rolls of mulch.
A description of the photodegradable
process follows (Fanton, Gazel and
Lemaire, 1984):
The coordination compound absorbs
photons coming from the ultraviolet
96
radiation of the sun, originating free
radicals. These react to the polyethylene
chains creating macro-radicals, which
oxidate forming groups, which in turn
absorb sun photons. This succession of
photochemical reactions causes a rupture
in the polymer chain. In sum, it is a fairly
rapid photofragmentation of polyethylene
chains, depending upon the luminous
intensity absorbed and the concentration
of the absorbent additive in the field.
Degradation starts with the appearance
of tears on the film: the plastic crystallizes
and fractures.
We were unable to gather precise
information on the minimum size of
polyethylene chains after the degradation
process. It's likely that these inert chains
aren't bio-assimilative due to their length,
(more than 35 carbons).
Buried film edges can't receive UV
radiation and are not photodegradated
during the cultivation year, and won't be
unless they reach the surface in the course
of subsequent years. Muddy film can
inhibit the degradation process described
above, so it's easy to find remains of these
buried edges a long time after their first
use.
PVC-based plastic film
Base polymer for this mulch is polyvinyl
chloride, which comes from an oil ethylene
and chloride from marine salt. (Chloride
makes up 57% of the polymer.)
In its un-refined state, this polymer is
hard and must be plastified. This is
accomplished with vegetable or synthetic
plastifiers. PVC mulch films also contain
stabilizers (zinc, calcium, and sometimes
heavy metals such as nickel, cadmium
and lead).
In France there's only one producer for
this kind of plastic, he's been manufac-
ING. LE DU
turing film for agricultural mulching since
1985. His plastic films are 15 pm thick and
come in narrow 0.64 m strips, between
which a row of corn is planted.The distance
between two consecutive rows is 0.75 m. A
four row planting and mulching machine
holds four rolls of film.
The PVC plastic film manufacturer
states that all the components in his
product are registered for contact with
food. Theoretically, then, the film doesn't
contain heavy metals.
The degradation process followed by
this film is complex. On one hand it's a
biodégradation of the plastifiers, and on
the other, its a photo-oxidation: additives
disappear, the PVC chain fragments. In
this case we don't know either how small
the polymer chains can get, but they're
probably not bio-assimilated.
The degradation process of the film is
characterized by progressive peeling even
after the harvest. The film carries on worse
until it looses elasticity and becomes
fragile.
Buried parts also degradate, so the
soil is completely f r e e d of plastic,
which isn't the case with photo-degradable
film.
Studies of various factors relative
to corn plasticulture
The following results come from experiments performed at the CEMAGREF of
Montoldre, in the Department of L'Allier,
JEAN
France, where corn cropping in uncovered
soil and under plastic mulch are practiced
on light, washed, drained soils with a low
water reserve.
The results concern:
- solar radiation energy,
- soil temperatures under plastic mulch,
- the evolution of soil water content.
Solar radiation energy
Photodegradation of a polyethylene
sheet is linked to the amount of ultraviolet radiation provided by the sunlight absorbed by the film. Measurements
were taken with the aid of two pyranometers. One was placed on one of the
plastic strips in the corn field 0.3 m from
the surface. Solar radiation energy
is given in kilojoules per square meter.
With this device it was possible to know
the amount of solar radiation received by
the plastic. This value was then related to
the value captured in a nearby meteorological station also equipped with a
pyranometer.
Results show that during the first forty
days of the vegetative cycle of the corn, the
plastic film received the same solar energy
as the station. After the first 55 days of the
cycle, however, energy for the plastic sheet
isn't more than 50%. This decrease is
related to the vegetative development of
corn and the height of the plants over the
mulch. (Between June 10 and 30, 1986,
mulched corn grew 6.4cm/day.)
97
Corn plasticulture
in
France
PERCENTAGE OF SOLAR ENERGY RECEIVED BY THE MULCH WITH
RESPECT TO THE SOLAR RADIATON ENERGY EMITTED EVERY DAY
%
110 100-
9080-
\
70-
fiO-
Î t
I 3 m.
HEIGHT OF CORN PLANTS
60-
t.,
\
130 cm.64
DATE
5/5/86
165/86
19/5
20/5
21/5
22/5
23/5
26/5
27/5
10
15
104,7 %
94,8 %
101,5 %
92,8 %
106,1 %
99,7 %
102,4 %
101,0 %
20
25
28/5
29/5
30/5
2/6
3/6
4/6
5/6
6/6
30
5/6
100,6 %
99,7 %
102,2 %
102,8 %
103,6 %
102,3 %
104,8 %
101,2 %
10
15
20
9/6
10/6
11/6
12/6
13/6
16/6
17/6
186
25
30
100,6 %
100,2 %
98,8 %
96,8 %
105,7 %
105,7 %
97,4 %
95,3 %
19/6
20/6
23/6
24/6
25/6
26/6
27/6
30/6
13
to
14
15
to
16
97,3 %
97,3 %
77,2 %
66,8 %
65,7 %
53,1 %
59,7 %
49,7 %
Example from 9/6/86
T. U. in hours
4
to
5
5
to
6
E n e r g y r e v e i v e d by
t h e s h e e t in
kilojoules/m2.
E n e r g y received b y
t h e meteorological
s t a t i o n in
kilojoules/m2.
Energy %: plastic
sheet/meteorological
station
6
to
7
7
to
8
8
to
9
9
to
10
<
98
11
to
12
12
to
13
14
to
15
16
to
17
17
to
18
18
to
19
860
300
1,584 2,400 2,829 3,151 2,903 3,192 3,037
120
510
1,270 1,840 2,450 2,840 3,050 2,780 3,060 2,950 2,600 2,110 1,520
86,0
97,9
99,6
Total energy received by the station between 0H00 and 24H00
from
7H00 to
14H00
Total energy received by plastic sheet from 7H00 to 14HOO
Energy %: plastic sheet/meteorological station from 7HOO to 14H00
*
10
to
11
103,3 104,4 104,3 102,9
28,410 kilojouleVm2.
18,970 kilojoule^m2.
19,096 kilojoule^m2.
100,6 %
ING. LE DU JEAN
Soil temperatures u n d e r plastic
mulch (greenhouse effect)
vered soil. This shows the significance
of the greenhouse effect caused by mulch
even in deeper layers of soil during
M e a s u r e m e n t s were t a k e n with the first 55 days of the crop; and also
thermocouples placed identically on the shows a fall in the thermal effect of mulch
soil at different levels under the plastic as soon as the plant displays foliage,
mulch and on naked soil (traditional crop). limiting the amount of solar radiation
Results indicate temperature differences reaching the ground. (In this case, on
at the same levels in mulched and unco- 15/06/86.)
C
SOIL
A V E R A G E T E M P E R A T U R E D I F F E R E N C E BETWEEN M U L C H E D A N D U N C O V E R E D
B E T W E E N 9 h 0 0 A N D 1 5 h 0 0 D U R I N G P E R I O D S O F 5 D A Y S A T A DIFFERENT LEVELS
( G R E E N H O U S E EFFECT)
10 »
8>
LEVEL O c m
(SOIL SURFACE)
6
S
LEVEL - 1 0 c m
»•
3
LEVEL - 2 0 c m
2 »•
• LEVEL - 6 0 c m
DATE
5/5/86
10
20
25
25
EVOLUTION O F WATER IN THE SOIL
% O F WATER IN THE SCHL
JUNE 78.000 m m
PLUVIOMETRY - JULY 3 0 , 0 m m
A G O S T 26,4 m m
24/5/85
|
30
31/6
y6/85
25/630/6
1/7
8/7
___
—I—i—i—I
16 2023/7
26
n
1
31/7 6
1/8
1—
8
P 30
31/8
2/09
99
Corn plasticulture
in France
The results shown here are from the
1985 experiment. Water content in the
soil was measured through soil samples
taken between 0 and 30 cm, 30 and 60 cm,
60 and 90 cm with the help of a drill.
Samples were taken from a mulched plot
and a traditional (uncovered) witness.
Water content was measured by two series of four tensiometers placed close to
the sampling area at 30, 60, 90 and 120
cm.
Level 0-30 cm. Water reserves in the
soil during June were enough to feed corn
under plastic mulch. It seems that during
the first month, the amount of water
retained by the soil was more significant
than that in the witness soil. The plastic
film formed a barrier limiting evaporation.
However radicular exploration of corn
under the mulch was more important than
for the witness. Indeed, the strong
development of mulched corn caused a
greater need for water. After June 25, the
difference in mulched soil water content
as opposed to that in uncovered soil
increased. After July 18 the 0-30 cm layer
of mulched soil had no water left for the
plants. This date is marked by a fall on the
tensiometer graph. On the witness plot,
tensiometer fall was July 28, that is, ten
days after.
Level 30-60 cm. Water content in
mulched soil was lower than in the witness.
The significant growth experienced by
mulched corn created a greater water
demand. Soil water was absorbed by a
more deeply developed and deep radicular
system; hence lower water content at that
level. By the first days of August, the
combined effects of this greater water
demand and the drought, resulted in water
depletion at that level for mulched soil.
This development is attested to by the
tensiometer drop at that level. This lack of
water for the plants since the first week of
100
August at the 0-60 cm level proves the
weak water retention capacity of these
lixiviated to "psuedogley" drained soils.
The evolution of the relative curve at
the 30-60 cm level in the witness corn crop
indicated that by the first days of August,
water content was the same as in the
mulched crop. This only proves the poor
water retention of these soils.
60-90 cm level. The effect of the drought
can be appreciated by the beginning of
August, but the mulched soil was more
humid than the witness at this depth.
Several reasons can explain this higher
water content: the strong development of
the corn cast more shade on the ground.
The consequentially un-degraded film
served, throughout the experiment, as a
barrier which limited water evaporation.
Two series of three tensiometers were
used in the 1986 test. These were placed
on mulched corn: one on the irrigated part
of the plot, another on the non-irrigated
part of the plot (to study the 60, 40, 20 cm
levels under the mulch.) It rained between
May 12-23, right after planting. 88.6 mm
of rainfall completely replenished the
water reserves in the soil. A dry period
followed in June (12.4 mm pluviometry),
and in July (14.4 mm pluviometry.) The
curves made by the values set by the
tensiometers show the evolution of water
in mulched soil:
The 0-20 cm layer dried quickly between
June 15 and 25 on non-irrigated mulched
corn.
The 0-40 cm layer dried just as fast
between June 20 and July 5.
The 0-60 cm layer dried slower between
July 10 and August 10.
Falls in the tensiometers at the three
levels occurred on June 25, July 11 and
August 12, respectively.
On irrigated mulched soil, water
evolution in the soil proved comparable to
ING. LE DU
% WATER IN THE SOIL
JEAN
SOIL (0-60 c m ) WATER EVOLUTION UNDER PLASTIC MULCH
0-60 c m
0
TENSIOMETER
(CENTIBARS)
13
NOT IRRIGATED
IRRIGATED
l n
*,
20
D = Tensolmeter
fall
- 6 0 cm
1/6/86
1
4.6
7,8
IRRIGATIONS
ACUMULATIVO
DE TEMPERATURAS
1/9/86
1/7/86
0.0
4,2
14,4
J_
1
J
2,5
L
17.0
1
27,2
H—PLUVIOMETRY (mm)
9,0
I
ACUMULATIVO DE TEMPERATURAS BASE 6 2 C Y FECHA DE FLORACION
(50% PANICULAS FEMENINAS)
1500 J
1000 I
LG 2 2 5 0
S E G U N D A SIEMBRA
PLASH F I C A D A
.
IRRIGADA
500 H
LG 2 2 5 0
PRIMERA SIEMBRA
PLASHRCADA
IRRIGADA
LG 2 2 3 0
IRRIGADO
FECHA
MAVO
1986
JUNIO
JUÜO
17/7 30/7
AGOSTO
SEPTIEMBRE
9/8
101
Corn plasticulture
in France
that of unmulched and non-irrigated soil,
except that it was slower.
The curve for the -40 cm level shows
the influence of irrigations, but it was inevitable the soil should dry. Tensiometers
fell on August 1.
On a year with a dry summer this kind,
of permeable soil has insufficient water
retention to optimize corn plasticulture,
therefore, irrigation is a must.
These results on water evolution in
mulched soil show how important it is to
know the water reserve (RU) or the readily
usable water reserve (RFU), in the soil
when corn plasticulture is contemplated.
In France we can observe that north of La
Loire a n d n o r t h e r n Picardy, corn
plasticulture is only practiced on deep
plots which are cold in the spring, and
have enough RU or RFU (between 100 and
120 mm of water.)
When a crop manufactures a kilogram
of dry weight, it means that approximately
600 liters of water are extracted from the
soil. The twelve tons of dry weight produced
in a hectare of corn, for example, require
7,200 m 3 of water per hectare; that its,
approximately 720 mm. These 600 liters
per kilo of dry weight must be increased
50% south of the 45th parallel (Bordeaux,
France) and 100% south of the 40th parallel
(Madrid, Spain.)
Soil RU and RFU are measured and
calculated (See Soltner document: The
Soil) by measuring the apparent soil
density, Da; the equivalent humidity, He;
and estimating the depth of the soil
exploited by the roots, P. The formula is
RFU in mm = 3.Da.He.P.
The disadvantages
of corn plasticulture
There aren't very many, and they are
mainly related to ecology; particularly
102
accumulated plastic waste in the soil when
photodegradable plastic is used. Indeed,
it's not unusual to find in a crop almost
intact strips of plastic, after a rake has
passed by, fracturing already fragile plastic
into small pieces. Polyethylene fragments
return to the soil during preparation and
end up saturating the layer being tilled.
This, without considering the buried strips
that once held down mulch, which haven't
degradated.
The aforementioned, however, isn't
the greatest disadvantage of corn plasticulture. Indeed, the plastic cover over half of
the cultivated surface can remain intact
during the vegetative cycle of the corn and
become a handicap to the plant.
In dry summer years and on light soil,
completely dry soil 0-40 cm under the
mulch doesn't consititute a good element
for optimum corn development, since it
limits air-soil exchanges. It is therefore
imperative t h a t photodegradable low
density polyethylene mulch function as
intended, effectively degradating two
months after its placement. At present,
this LDPE mulch degradating process
seems to be well mastered by manufacturers. But the problem arising from buried
parts still remains to be solved.
Advantages of corn plasticulture
The a d v a n t a g e s are m a n y when
pedoclimatic conditions are adequate.
The plant benefits from the greenhouse
effect, that is:
- soil temperature increase,
- limited soil evaporation.
The soil maintains its structure (zero
battance on lime soils)
Plastic mulch increases heat which
accelerates corn development, making for
quicker germination (precocity after 5
days, approximately), faster vegetative
ING.
development (corn vegetative cycle
advances approximately 3 weeks), deeper
and faster radicular growth, which benefits
water utilization. This precocity afforded
by mulch makes it possible for feminine
panicles to bloom before soil water reserves have been exhausted. In most cases,
this precocity generates higher yields
whether in grain or whole plant dry weight.
In Britanny the most complete study
LE DU
JEAN
done on increased yield and dry weight for
silo was carried out by the Reseau National
D'Experimentation et de Demonstration
(RNED) Cereales. Thirty tests were
performed from 1983 to 1985 (12 reference
plots, two of which were in the Armor
coasts) to measure the effect of mulch on
silo corn production, with the same
varieties used on naked soils and with
later varieties.
Compared silo corn production of mulched and naked soil
Later varieties
Same varieties
55
31
Number of comparisons
+ 4.4 t MS/ha
+ 3.4 t MS/ha
Increase in mean yield
+ 4.9 %
+ 3.8 %
Average increase in dry weight content
Source: R N E D C e r e a l e s B r e t a g n e , 1986.
Increases in yield vary greatly from
one test to another. In varieties with
different precocities, this can be nil or over
9 t m$/ ha. These different results are
brought about by a combination of different
f a c t o r s : region a n d selected plots,
C O M P A R E D YIELD BETWEEN M U L C H E D / N A K E D
( U S I N G LATER VARIETIES F O R PLASTICULTURE)
L-UIYIKAIÎbUINS
+ 0 + 1
experience with the technique. Other
studies, such as the one made by the EDE
on the northern coasts in 1981, 1982 and
1983 (Blondel, 1984) highlight the great
differences in yield increases obtained
thanks to mulch.
+2
+3
+4
INCREASE
+5
+6
I N YIELD ( I N
+7
+8
SOIL
+9
+10
MS/HA)
103
Corn plasticulture
in France
There is also an increase in yield for the
grain harvest. These experiments aren't
as in-depth as those performed on whole
plants for silo. Using the 1986 Montoldre
experiment as an example, we had an
average increase of 6.6 points of dry weight
and 1,880 kg of grain dry weight per hectare
of mulched corn with respect to the witness.
Expressed in commercial grain amounts,
mulch produced an increase of 22 quintal^
ha with respect to the witness in this
experiment. We found a more important
gain in production, an earlier harvest date,
and a greater amount of dry weight for the
grain corn.
However, generally speaking, it seems
that plasticulture is less important for
grain corn than for silo corn, and that the
ratio of ears on a whole plant doesn't
always improve; but this remains to be
proven.
These gains in yield require an increase
in fertilizers.
animal raisers contemplate plasticulture
as insurance against lack of silo reserves
and a guarantee of good quality silo corn.
This insurance, however, is difficult to
calculate.
Nevertheless, plasticulture can't be
systematically recommended, given the
wide diversity of results. An interesting
study carried out in Britanny by RNED
Cereals compared, in the course of three
years, more than thirty cultivation tests
on naked and mulched soil, including two
varieties with different precocity and two
sowing techniques.
DIFFERENCES IN YIELD DUE TO
MULCHING
Economical aspects
In contrast to traditional cropping, this
t e c h n i q u e implies a more or less
substantial extra cost depending upon the
exploitation.
Amortization of these costs requires a
yield gain between 16 and 23 dry quintals,
in the case of grain corn, and between 3.3
to 4.7 tons of dry weight in the case of silo
corn. Investment amounts to 2500-2700
francs per hectare including plastic film,
machine sowing and additional fertilizers
necessary to achieve expected increase in
yield and financial costs. Traditional crop
costs are deducted from this total.
Following this line of thought, the yield
increase should free hectares so they can
be dedicated to other crops. Margin from
the latter crops should be higher than the
cost of plasticulture to free said land. Many
104
This figure shows yield differences in
one variety due to mulch. It can be observed
that yield is improved with mulch, but
also that in 62% of the cases, yield is under
the 3.5 tons of dry weight which constitute
the economical minimum.
ING. LE DU
It can be seen that in spite of the
benefits of this technique, when the grower
decides to apply it, he must be aware of the
financial risk involved. It should be noted
that at present, the grower wishing to
apply corn plasticulture can find support
with a better pedoclimatic knowledge,
particularly with respect to clay, lime,
humus and RFU percentages, as well as
v a r i e t y selection a n d t e m p e r a t u r e
calculations. If experimentation were
carried out today, the cloud of doubts would
be narrower.
Conclusion
Corn plasticulture is developing in
France. Until now, however, it is mainly
concentrated in the northern and western
part of the country, and more attractive to
silo corn growers than to grain producers.
Techniques consist in mulching with
wide photodegradable LDPE plastic film
or narrow biomechanodegradable PVC
s t r i p s . Available sowing-mulching
machines are adapted to both techniques
and work smoothly. Their operation,
however, must be slow and require an
JEAN
experienced driver.
Greater progress is possible. Present
research is geared toward reducing the
amount of plastic used and also to decrease
weeding. At present, plots are weeded
prior to planting. A second weeding is
carried out during early development of
t h e p l a n t s w i t h a p r o d u c t called
"Dinoterbe", which can penetrate the
plastic sheet. It's very likely, though, that
this product will be banned in the near
future.
Regarding the environmental point of
view, photodegradable plastic leaves
problematic residue in the soil. A new corn
plasticulture method is under trial. It
consists in using non-photodegradable
polyethylene which could be removed
during the seven-leaf stage of the plant
with a machine capable of pulling it out of
the earth, cleaning it, and rolling it (DBE)
at a rate of 6.5 km/h without damaging the
plants. Trials are being carried out with
17 pm plastic films, with the hope of
eventually using a 12 pm film.
Plasticulture, therefore, is not a static
technique and allows new developments.
105
Corn plasticulture
in France
Bibliography
Culture du maïs en Champagne
crayeuse
avec films
plastiques
photodégradables.
Cahier
des
ingénieurs agronomes, n 2 306, Mai
1976.
DUTIL, P .
La photodégradabilité contrôlée
des films de polyéthylènes agricoles en
Israël. Plasticulture, n2 30, Juin 1976.
sol. Production laitière moderne, n 2 145,
Février 1986.
DESPLANTES,
LE
Du,
WIERZBICKI.
Plasticulture du maïs. BTMEA, n s 7-8,
Juillet-Août 1986.
GILEAD, D .
Les bases de la production
végétales. Tome 1: le sol.
SOLTNER, D .
Les applications agricoles
et horticoles des films de polyéthyléne
(PEbd) photodégradables. Plasticulture, n 2 41, Mars 1979.
Atlas agroclimatique saisonnier de la
France, 1980.
HANRAS, J . C H .
GAZEL ET LEMAIRE. Fiabilité du
film photodégradable agricole. Caoutchouc et plastiques, n2 641, Mai 1984.
LE DU, J. Photodégradation des films
plastiques en semis. BTMEA, n2 22,
Octobre 1987.
La plasticulture du maïs en Bretagne.
Document du Conseil Général des Côtes
d'Armor-Mars 1992.
M. Les équipements
de
plasticulture. Motorisation, Novembre
1993.
Nouveautés - Désherbage - Résultat des
variétés. Entraid, Janvier 1994.
POTTIER,
FANTON,
Deux facteurs limitants pour le
maïs: la température et la structure du
PERROT, M .
106
Mais: adapter la variété à la
parcelle. Top Culture, n 2 33, Janvier
1994.
Carte des sols et des sommes de
température. Document Maïs Adour.
VERSANTI, L .
Web vegetable
cultivation as
compétitives tools
ING. ALEJANDRO GÁLVEZ
Invernamex
INC. ALEJANDRO
. ^ ^ n extremely ample and varied range of
possibilities is available through the use
of plant tissue cultivation techniques (i.e.
micropropagation), not only because of
the complexities of the process, but because
of their applications. It is here where
several aspects come together. First the
application should be evaluated so the
producer pays its total cost; second, it is to
be carried out in a way that is comprehensible to the producer and practical
within the production system he may have.
Finally, the value of the material plus its
implementation in the production system
must be affordable, and provide benefits
making it more productive.
Producers face a series of problems
which t h e y m u s t solve d u r i n g t h e
production process. I'm referring to biotic,
edaphic and climate related problems.
Some of these can be dealt with beforehand,
and others, as they arise. Nevertheless,
the economical success of the crop will
depend upon a satisfactory sale of the
production, which is why we never know
how much we'll be making until the last
day of the sale.
It is clear that problems during the
production process, cause reductions in
yield and, very likely, in quality. This
makes us liable to countless risks, which
are very hard to measure and that we
GÁLVEZ
learn to prevent with every cycle.
Each exploitation must be considered
as a profitable, well managed, business.
In the farming business, producers have
to take into account several sensitive
issues, which u s u a l l y pose control
problems. These are costs, losses and risk
prevention.
We'll briefly examine these three
concepts to identify their consequences
and the essence of quality.
The quality of agricultural species, from
my point of view, is poorly understood and
analyzed in essence, since we seek better
quality in order to sell the final product.
However, final quality is a response to
every moment of the production process,
and depends upon the quality of the labor,
production techniques and response to
unforeseen difficulties.
Final quality not only implies a better
sale and price, but also t h a t during
production there were fewer losses, more
efficiency, technical capacity and a better
use of resources. This, logically results in
lower production costs and higher profits.
A lot has been said about the benefits
t i s s u e cultivation can give to any
production, nevertheless it has been
scarcely understood. In almost any
publication we can read about t h e
advantages of these techniques and how
109
Web vegetable cultivation
as competitiones
tools
they interrelate with costs, losses and risk
a p p r a i s a l . The following are some
examples:
- Genetical homogeneity.
- Disease-free plants.
- Potentially productive plants.
- Better response to collateral technologies.
- Selection of outstanding plants.
- Quick multiplication.
- Simplification of genetical improvement processes.
- Higher quality.
- Recovery of original characteristics.
- Higher production.
- Lower production costs.
The relationship between these technologies and competitiveness for the
producer and the nation is evident.
Regarding Mexico, the following aspects
are worth mentioning:
Ecology. Tissue cultivation companies
can produce millions of plants in a
relatively small space. Even the smallest
lab has to produce between two and three
million disease-free plants.
Technological development. These lab-
si
110
companies absorb information on and
specialize in problems proper to each crop.
Afterwards, they furnish very precise
information on production systems that
are both safe and profitable.
Plant health. The production systems
and goals of these labs adhere to legislation
set forth by the Mexican Agricultural and
Water Secretariat, with who they share
equal goals in favor of the public.
Germ Plasm. Little has been achieved
in this country along these lines, and there
is still a strong dependence on international sources. Plant tissue laboratories
should therefore have their own germ
p l a s m b a n k , which is e s s e n t i a l to
commercialization purposes and for
resource optimization. In certain cases
they will have to implement genetical
improvement in t h e search of new
varieties.
The consolidation of a strong relationship between production processes and
plant tissue cultivation techniques will
result in more productive businessmen,
more profitable businesses and competitiveness for all Mexicans.
Automatization
of irrigation
and nutrition
equipments
ING. A V I IVANIR
Training and Service in Latin America
ING. AVI
1. Physical structure (cables, solenoids,
water meters, fertilizer meters,
valves, etc.
2. Maintenance (operation and
maintenance).
3. Choice of the adequate system.
The advantages of irrigation
automatization
1. Savings in water consumption.
2. Savings in energy consumption.
3. Savings in transportation.
IVANIR
4. Savings in labor.
5. Increases f e r t i g a t i o n efficiency
(through better pressure, wind and
humidity conditions, among others).
6. Increases fertilization efficiency.
7. Improves retro-washing efficiency.
8. Sampling in true sensor time.
9. Irrigation emergency programs, in
the case of frost and heat waves.
10. Better pump operation.
11. Data concentration.
12. Network safeguarding.
113
Diseases
and soil solutions
D R . ALBERT O . P A U L U S
P l a n t P a t h o l o g y , U n i v e r s i t y of C a l i f o r n i a
DR.
S o i l fumigation is practiced on various
vegetables and strawberry crops in the
United States of America. During the 194050's growers usually planted two to four
successive crops and then moved on to
new virgin ground. But the virgin land
gradually became unavailable to growers
because of housing and commercial
developments and the prohibited cost of
clearing what virgin land was availabe.
New irrigation systems were costly to
install on the new lands. This lead to a
condition known popularly as "old land
disease", which was thought to be due to a
complex of fungi, nematodes, weeds and
deterioration of soil physico-chemical
properties. This lead to decreased tomato,
strawberry, etc. yields with successive
crops. Full scale fumigation of tomato fields
in Florida was too costly yet in-the-row
fumigation for short-term nematode control proved inadequate for long season
t r e l l i s - g r o w n t o m a t o e s in Florida.
Research showed that polyethylene films
used as mulch could enhance the performance of fumigants on large acreage
(Bewick, 1989).
Soil Fumigants
Methyl bromide (bromomethane) is one
of the most commonly used fumigants for
ALBERT
O.
PA ULUS
the control of fungi, nematodes, soil insects,
weeds and has some effect on bacteria and
virus. It is a colorless, odorless, highly
poisonous gas. To prevent hazards, 1-2%
chloropicrin (tear gas), a lachrymator, is
added as a warning agent. The material is
compressed as a liquid and is marketed in
small metal cans or in large cylinders. A
polyethylene sheet is immediately placed
over the treated area during the soil
injection process and allowed to remain
for at least 48 hours, when soil temperature
is about 152 C. If the temperature is below
152 C the exposure time should be extended to e n s u r e a d e q u a t e f u m i g a n t
dispersion. Many California growers leave
the polyethylene sheet on for a least 7 days
and sometimes longer during cool weather
of the winter.
Chloropicrin (trichloronitromethane) is
highly effective for the control of fungi and
soil insects; provides good control of bacteria and nematodes but poor control of
weeds. Large stocks of chloropicrin were
left over from World War 1 and investigations showed the fungicidal, bactericidal
and n e m a t i c i d a l p r o p e r t i e s of t h i s
chemical. As with methyl bromide soil
fumigations, a polyethylene sheet is
immediately placed over the treated area
during the soil injection process. The
polyethylene sheet prevents damage from
117
Diseases and soil
solutions
drift of fumes to neighboring crops and
hinderance to man. Soil fumigation with
chloropicrin should not occur when soil
temperatures are below 10aC. The treated
land should be left undisturbed for a least
two weeks during summer and at least
three weeks in winter. If after these periods
the fumigant still persists in the soil, as
indicated by odor or eye irritation on close
examination, the land should be disced or
plowed to help aeration (Vanachter, 1979).
Mixtures of methyl bromide/chloropicrin are commonly used in the United
States for the control of soil pests.
Chloropicrin and methyl bromide act
synergistically. A combination of the two
fumigants provides excellent control of
many plant soil pests.
Metam sodium (sodium-N-methyldithiocarbamate) provides excellent control
of nematodes and good control of fungi,
weeds and soil insects. It is sold in the
United States under such trade names as
Vapam or Soil-Prep. Metam-sodium is sold
as a liquid which is soluble in water,
producing a strong odor. Applied to the
soil, it is converted into methylisothiocyanate (MIT). Metam sodium can be
injected into the soil, applied by drenching,
used in sprinkler systems or placed
through drip irrigation lines. The variability of results with this compound has
been a world-wide problem. Experi-ments
continue in 1994 to develop the best method
of applicatin for effective control.
Dazomet (3,5-dimethyltetrahydro-1,3,5
(2H)-thiadiazine-2-thione) is sold as a
finely granulated product under the trade
name of Basamid. The chemical when in
contact with moist soil hydrolyses to
methylisothiocyanate. Basamid is not
registered for use on any food crop in the
United States at the present.
Telone II (1,3-dichloropropene) is an
excellent fumigant for the control of nema118
todes and provides good control of some
soil insects. It is not effective for the control
of fungi, bacteria or weeds. Telone C-17
contains 1,3-dichloropropene + chloropicrin and is effective for the control of nematodes, some soil pests and certain soil
borne diseases. Telone II is not registered
for use in California at the present time.
Activity of fumigants in soil
The important factors influencing the
movement of soil fumigants are the
chemical and adsorptive characteristics of
the toxicant, t e m p e r a t u r e , moisture
organic matter, soil texture and soil profile
variability. Assuming the same soil profile
and soil conditions at equivalent rate, the
fastest and far reaching fumigants are, in
o r d e r of activity, m e t h y l bromide,
chloropicrin, 1,3-dichloropropene, and
methylisothiocyanate, respectively.
Soil fumigants, with the exception of
MIT (methylisothiocyanate), are applied
10 to 90 cm below the soil surface as a
liquid or gas. The first process that takes
place in w a r m soils is t h e i n i t i a l
vaporization of the chemical from liquid
phase to the gaseous phase. The individual molecules now have an affinity for,
and may be removed from, the pore spaces
by the water, mineral, and organic phases
of the soil. Since the diffusion of the gas is
greater in air above the soil surface than
with the soil system, upward mass flow
and diffusion is greater than downward
movement. Also, diffusion is unaffected by
gravity. Therefore, seals of some sort are
necessary at the soil surface to retain
diffusing molecules long enough to give
maximum effectiveness against organisms
located near the soil surface (Munnecke,
Van Gundy, 1979).
The vapor pressure, or the rate at which
the chemical leaves the liquid phase, is
DR.
important in determining the movement
of fumigants in soil. If the vapor pressure
of the liquid is high, as in the case of MB
(methyl bromide), the gaseous concentration of the chemical in the soil pore spaces
increases so rapidly that movement of the
chemical occurs first by mass flow and
then by diffusion.
The vaporized molecules of soil fumigants tend to be dissolved in the soil water
films. There is a continuous reestablishment of a dynamic equilibrium between
air and water. This equilibrium is governed
by Henry's Law, which states that the
ratio of the concentration of the fumigant
in the soil water to the concentration of the
fumigant in the soil air is a constant at a
given temperature. The vapor pressure
and solubility of MB in water is high. If the
soil water content for any fumigant is
increased, both the rate of movement is
slowed and the distance traveled in the
soil pores are reduced.
The characteristics of MIT are lower
adsorption, relatively greater partition into
water from air, slower diffusion, and higher
decomposition rate at high temperatures,
as compared with other soil fumigants.
These factors probably are responsible for
its relatively poor control of organisms in
large soil masses.
Solubility is important because most
soil microorganisms are bathed in water
films protecting them from direct contact
with the fumigants in vapor phase. The
toxic molecules must be present in the soil
solution in which the target pest is bathed.
Moisture is important in the adsorption
of fumigant on soil particles. Soils at or
dryer than the wilting point (-15 bars)
have few or no water molecules surrounding the soil particles and adsorption of
the fumigant molecules directly to the
particle surface is increased. In moist soils,
adsorption is reduced. In general, accepta-
ALBERT
O. PA ULUS
ble toxicant movement is best in moist
soils with a water potential of -0.6 to -15 bar.
Polyethylene t a r p s of 25-100 pm
thickness are used for MB and chloropicrin
fumigations to slow loss of fumigants to
the atmosphere. Compaction of the soil
surface or the application of water seals
are used with less volatile fumigants such
as MIT.
Usually, fumigant effectiveness increases with increase in temperature. Fumigants such as MB are not very effective in
soils at temperatures below 10aC. A
mixture containing 25,000 ul MB per liter
of air was circulated over mycelial colonies
of Pythium ultimum held for varying
times at 5 temperatures between 52 and
30s C, inclusive. It required approximately
3.8 times more MB to kill 90% of the
fungus propagules at 52C than at 302C.
Soil fumigants are not always enhanced in
warmer soil as compared to cold soils.
Experiments in Georgia for the control of
nematodes with vapam (SMDC), mylone
(DMTT),l,3-dichloropropene and MIT
when soil fumigated in the winter time
concluded the best results were obtained
when soil temperatures were below 162C,
but above 02C. The reasons for this result
were not known.
Soil texture is often directly related to
the success or failure of a field fumigation.
Generally, coarse-textured soils (sandy
loams) are easy to fumigate successfully,
whereas fine-textured soils such as clay
loams and clays, are more difficult to
fumigate successfully. The soil texture on
many agricultural soils varies with depth.
Agricultural soils may have clay lenses at
various depths, or they may be compacted
below the surface. Either of these factors
seriously affects downward diffusion of
soil fumigants (Munnecke, Van Gundy,
1979).
119
Diseases and soil
solutions
Tomato soil fumigation trials
Soil fumigation is a common practice in
sandy soils repeatedly planted to tomato
in Florida. Trials were initiated to compare various soil fumigants for the control
of Fusarium wilt (Fusarium oxysporum f.
sp. lycopersici) race 3, Fusarium crown
rot, (Fusarium oxysporum f. sp. radicislycopersici), stingnematode (Belonolaimus
longicaudatus), awl nematode (Dolichororus heterocephalus), stunt nematode
(Tylenchorhynchus
spp.) and root-knot
nematodes (Meloidogyne incognita). Beds
were constructed 20 cm high, 0.76 m wide
on 1.4 m centers. Three streams of each
chemical were injected 15 cm deep on a 20
cm center into 7.7 m single bed plots.
Whitq/black laminated plastic fil (1.25 mil)
was sealed over the bed as each plot was
treated. Soil moisture (0-15 cm deep) at
time of treatment in the fall and spring
was 10.5% on a dry weight basis. This was
roughly field capacity. Results are shown
in Table 1.
Table 1
Yield response of tomato to soil fumigants applied to Eau Gallie fine sand
Yield (tons/1000 row ft.)
Fusarium wilt Fusarium crown rot
Treatment
Rate/Acre
Fall 1983
Methyl bromide 99.5%
+ chloropicrin 0.5%
400 lb.
5.33 a
4.67 a
Methyl bromide 67% +
chloropicrin 33%
350 lb.
4.79 ab
4.03 a
30 gal.
4.14 b
2.91 c
4.04 a
2.58 b
Vorlex
No treatment
-
(Vorlex-Methylisothiocyanate 20% + chlorinated C3 hydrocarbons 80%
Significant 5% level
Spring 1984
Methyl bromide 99.5%
+ chloropicrin 0.5%
400 lb.
5.09 a
4.72 a
Vorlex
35 gal.
4.38 b
4.51 a
Methyl isothiocyanate
40% (Trapex 40)
25 gal.
4.16 b
3.97 a
-
2.12 c
2.72 b
No treatment
Significant 5% level
DR.
All treatments increased tomato fruit
yield and reduced populations of sting,
stunt, awl nematodes. Root-knot nematodes were suppressed by all treatments.
All treatments reduced Fusarium wilt race
3 and Fusarium crown rot. A greater
number of plants showed symptoms of
Fusarium wilt at pH 5.5-6.0 than at pH
7.0-7.5; soil pH had no effect on incidence
ALBERT
O. PA ULUS
of Fusarium crown rot (Overman, Jones,
1984).
Jones and Overman in 1985 compared
various soil fumigants for the control of
root-knot nematode and Verticillium wilt
(Verticillium dahliae) at soil pH of 5.5 and
7.5. Low and high soil pH plots were
established by using sulfur or hydrated
lime.
Table 2
Effect of soil pH and soil fumigants on the percentage of "Sunny" tomato
tomato plants with root knot and verticillium wilt
Root-knot
Verticillium wilt
Treatment
Rate/Acre
at soil pH
at soil pH
5.5
7.5
7.5
5.5
Percent
Methyl bromide 67%
350 lb.
0
3
14
6
+ chloropicrin 33%
Methyl bromide 98%
+ chloropicrin 2%
300 lb.
1
7
6
Metam-sodium
50 gal.
32
87
7
25 gal.
Vorlex
28
17
22
No treatment
46
93
17
(Metam sodium - 32.7% sodium N-methyldiothiocarbamate)
71
58
90
-
The high pH encouraged development
of v e r t i c i l l i u m w i l t a n d root-knot
nematodes. Howewer, the injection of
f u m i g a n t s into t h e s e high pH soils
controlled Verticillium wilt and root-knot,
resulting in maximum fruit production. In
the same experiment raising the soil pH to
7.5 with hydrated lime in conjunction with
the use of nitrate-nitrogen and mulch also
greatly alleviated the severity of fusarium
wilt, fusarium crown rot and southern
blight, (Sclerotium rolfsii) and increased
0
yields (Jones, Overman, 1985).
Corky root (brown root rot) has been
recognized as an important disease of
tomatoes in glasshouses in Europe for
many years. Corky root also occurs on
processing and fresh market tomatoes in
scattered fields in northern and central
California. The primary pathogen is
Pyrenochaeta lycopersici which has also
been recovered from nightshade (Solanum
nigrum). Corky root severity declined as
the transplanting date was delayed and
121
Diseases and soil
solutions
the soil became warmer in a trial by
Campbell, et. al., involving plants inoculated in the greenhouse and transplanted
to the field and noninoculated plants
transplanted into infested soil. Yield loss
estimates of up to 70% were made by
growers of processsing tomatoes, and
losses of the same magnitude occurred in
fumigation experiments with fresh market
tomatoes. A field trial in 1979 showed
chloropicrin (168 kg/ha) and methyl
bromide + chloropicrin (262 + 117 kg/ha)
effectively reduced disease severity,
increased plant size, and increased the
yield of large fruits. Neither methyl bromide nor ethylene dibromide + chloropicrin reduced disease severity or
increased yields significantly compared
with nontreated check. In a separate trial
metam sodium 935 1 of 33% metham
sodium per hectare, was tested as a drench
in the same field. Two treatments, with or
without a 1 ml polyethylene tarp over the
treated soil, were compared with the
nontreated check. The plants in metam
sodium treated soil were significantly
larger (5.8 and 5.9 kg/plant without or
with a tarp, respectively) than those in
n o n t r e a t e d soil (3.9 kg/plant). The
desease severity rating was reduced
signifi-cantly to 0.4 by metam sodium
with a tarp. Metam sodium without a tarp
had a disease severity rating of 2.9, which
was not significantly different from the
nontreated check with a disease severity
rating of 4.4.
Fumigants selected for the 1980 plot
were applied in October 1979. The chloropicrin and methyl bromide + chloropicrin
fumigants and tarp, if specified, were
applied by a commercial fumigation rig
that treated and covered a 3.4-m-wide
strip. The metam sodium was mixed with
irrigation water as it flowed through a
ditch onto each plot, where it was ponded
by earthen dikes and allowed to percolate
into the soil. Results are shown in Table 3
(Campbell, Schweers, Hall, 1982).
Table 3
Comparison of four soil fumigants applied for control of Pyrenochaeta
lycopersici in Greenfield sandy loam soil, Tulare county, CA in 1980
Treatment
Methyl bromide 262 kg
+ chloropicrim 117 kg/ha
Chloropicrim 168 kg/ha
Chloropicrim 168 kgTia
Metam sodium 935 1/ha
Tarp
Disease
severity
Yes
0.2 x
Yes
0.5 x
No
4.4 z
No
1.9 y
No treatment
No
4.8 z
Significant 5% level. Disease severity on five point scale.
Ns large
Plant +
Fruit (kg) fruits/plant
9.8 x
25.1 wx
9.9 x
27.4 w
18.6 y
6.6 y
7.0 y
3.3 z
21.0 xy
7.3 z
DR. ALBERT
Control of strawberry pathogens
In the field major requirements for
successful soil fumigation are excellent,
deep, fine soil tilth, somewhat less than
seed bed moisture throughout the soil and
soil temperatures of 139C and above. In
addition, dosage is also a function of the
degree of fungus infestation or inoculum
potential of the soil, a fact commonly
overlooked in commercial soil fumigation.
Data from the following experiment illustrate the point.
A field soil known to be heavily infested
with Verticillium was diluted with steam
soil in proportions of 1:1, 1:10 and 1:25.
This established three different levels of
Verticillium infestation in a uniform soil.
The soil was placed in cylinders in the
greenhouse, chloropicrin injected at rates
of 2, 2.5 and 2 ml, respectively, a check
series was added. 'Bonny Best' tomato
seeds were planted in the treated soil.
When the plants were 30 cm high, they
were read for symptoms of wilt and
cultured for Verticillium. The nonfumigated check soil gave a high infection
index in dilutions of 1:1 and 1:10, and
trace values in the 1:25 dilution; 1 ml of
chloropicrin (160 lb/acre) gave poor control of Verticillium in the 1:1 soil dilution
and excellent control in the 1:10 and 1:25
dilutions; 1.5 ml of chloropicrin (240 lb/
acre) gave excellent control of Verticillium
except in the soil surface of the 1:1 soil
dilution; 2.0ml (320 lb/acre) gave excellent
control throughout all soil dilutions except
for a trace in the surface soil of the 1:1
dilution. The data showed, and it has also
been our experience in the field, that it
requires more chloropicrin to achieve control of Verticillium in a heavily infested
field t h a n in a lightly infested field. Thus,
a required dosage is proportional to
quantity of fungus inoculum (inoculum
O.
PAULUS
potential) (Wilhelm, et. al, 1974).
Chloropicrin and methyl bromide act
synergistically. From field studies and
observations we know that a dosage of
200 lb/acre of chloropicrin sealed by water
or polyethylene film fails to control
Verticillium wilt. The low r a t e may
actually cause an increase in severity of
the disease. Methyl bromide at a dosage of
200 lb/acre favors the disease. A mixture,
however, composed of equal parts of
chloropicrin and methyl bromide giving a
rate of 200 lb/acre of each gives nearly
complete control of the disease in a wide
range of soil types and is one of the most
effective fungicidal soil fumigants ever
developed. This combination also controls
other injurious soil fungi, such as Pythium,
Phytophthora, Rhizoctonia, and Pyrenochaeta, and to soil-borne insects, nematodes and to both weed seed and dormant
weed structure. Weeds of the genera Malva and Alfilaria, and of the common
legumes, however, usually survive the
fumigation (Wilhelm, et. al, 1974).
Preplant soil fumigation allows us to
plant on the same land year after year.
Proportions of the fumigant components
may be tailored to individual field
requirements. Generally, the commercial
practice on land to be p l a n t e d to
strawberries and where Verticillium has
been controlled by previous fumigation, is
to use a 2:1 methyl bromide-chloropicrin
mixture and to reduce the dosage where
possible. In light soils the dosage may be
reduced more than in heavy soils. Thus to
control Verticillium wilt, 325-375 lb/acre
of the 1:1 mixture is required; for fumigation of the same land for a subsequent
planting of strawberries 275-375 lb/acre
of the 2:1 mixture generally gives adequate
results (Wilhelm, et. al., 1974).
Tests compared chloropicrin alone and
the mixture of chloropicrin, 2 parts, and
123
Diseases and soil
solutions
methyl bromide, 1 part, in a field
application. One section of the experim e n t a l a r e a was irrigated prior to
application of the fumigants and contained
12-15% of moisture a few inches belowthe
soil surface, or a little under 50% of the
estimated field capacity of the soil. An
adjacent but smaller section was dry and
cloddy. Applied to dry, cloddy soil, 480 lb/
acre of chloropicrin failed to control
Verticillium wilt. In the moist area of the
field the mixture of chloropicrin + methyl
bromide provided excellent control of
Verticillium at 320 lb/acre and covered
with a polythene tarp (Wilhelm, et., al.,
1961).
Chloropicrin and metam-sodium were
compared in England as a preplanting
treatment for the control of Verticillium
wilt of strawberry. Chloropicrin was
injected at a depth of 15.2 cm at 30.4 cm
staggered centers by a hand operated
injector. Each injection delivered 3.6 ml
(34.5 gal/acre) at the high dosage and 1.2
ml (11.5 gal/acre) at the lower. Plots were
rolled twice and then sealed with water.
Metam sodium was diluted with water
and applied at 330 gal/acre and 110 gal/
acre by a watering can with a fine spray.
The plots were rotavated after treatment.
Results are shown in Table 4 (Talboys,
Way, Bennett, 1966).
Table 4
The effect of soil fumigation on the yield of Cambridge Vigour
strawberry (means/plot)
Treatment
Total yield /lb) 1963 Total yield (lb) 1963
No treatment
29.1
107.8
Chloropicrin
34.5 gal/acre
34.9
135.6
Chloropicrin
11.5 gal/acre
29.1
135.6
Metham-sodium
330 gal/acre
29.8
126.2
Metham-sodium
110 gal/acre
32.8
119.2
S. E. mean
1.65
5.52
-
Johnson et. al., compared full coverage
vs. bed fumigation and compared Vorlex
with methylbromide/chloropicrin soil
fumigation in a field with fine sandy loam
soil which had been fumigated and planted
to strawberries the previous years. Soil
treatments were applied in early August
and plants were set in late August. The
cultivar was Lassen. Treatments compared a mixture of 2 parts of methyl bro124
mide and 1 part of chloropicrin at 225 lb/
acre, Vorlex (20% methyl isothiocyanate
+ 80% chlorinated C3 hydrocarbons) at 30
gal/acre with full coverage applications
and a bed aplication of methyl bromidechloropicrin at the rate of 225 lb/acre. All
treatments were tarped for 24 hours.
Results are shown in Table 5. (Johnson,
Holland, Paulus, Wilhelm, 1962).
DR.
ALBERT
O.
PAULUS
Table 5
Effect of fumigants and two methods of application on the yield of Lassen
strawberries-Summer planting, Los Angeles county
Number 12-pint trays/acre
Treatment
Gain over check
Total yield
Full coverage
Methyl bromide 67% + chloropicrin
33%, 225 lb/accre
3,679 a
1,682
2,523 b
526
Methyl bromide 67% + chloropicrin
33%, 225 lb/acre
2,946 b
949
Check
1,997 c
-
Vorlex 30 gal/acre
Bed application
Significant 1%
In England Harris compared chloropicrin and dazomet in soil fumigation
experiments for the control of Verticilllium
wilt of strawberry. Dazomet was applied
during September and the chloropicrin
applied in September/October. All plots
were covered with a single sheet of
polythene-nylon multilayer sheet of low
gas permeability. Results are shown in
Table 6.
Table 6
The effects of pre-planting treatments on yield in the strawberry cv Hapil
Dazomet
Chloropicrin
Control
450 kg/ha
210 l/ha
Yield (g plant)
372
1,055
989
1987
541
1,038
999
1988
Chloropicrin was marginally more
effective than dazomet for wilt control
(Harris, 1989).
Ridge fumigation was evaluated on
soil to be planted to strawberries and
infested with Verticillium dahliae as a
cost-saving alternative to overall soil
fumigation. A liquid fumigant injector
was developed to be able to ridge-up and
cover the ridge with polyethylene film in
a single operation. Ridge fumigation
treatments were applied in autumn, 1981,
Diseases and soil
solutions
at bed formation, using different rates of
both liquid and granular fumigants under
black polyethylene film (p50m). Dazomet
treatments were spread by hand just prior
to ridging and incorporated into the ridged
soil during ridge formation. The standard
treatment for comparison was overall
methyl bromide + chloropicrin soil fumi-
gation with a mechanized rig which was
done about 3 weeks before bed formation
and covering with a black film. Strawberry
plants cv. "Tioga" were planted through
the film 5 weeks later. Fruit yields are
shown in Table 7 for the 1981-82 and
1982-83 seasons.
Table 7
Effect of mechanized ridge-only soil treatments on 'Tioga"
strawberry yield for 1981-1982 and 1982-1983 seasons
Total yield (t/ha)
Application rate
Treatment
kg ai/ha
1981-1982
1982-1983
147
Chloropicrin
41.5
21.0
228
Dazomet
48.2
29.1
190
Dazomet
47.3
26.6
Methyl bromide + (overall)
chloropicrin
450
47.6 m
28.8
Methyl bromide + (ridge)
chloropicrin
138
38.3
16.1
24.1
4.3
7.1
4.7
Untreated
-
LSD 5%
The lowest dazomet rate used was
adequate for maximum response, whereas
similar rates of methyl bromide/chloropicirin were too low. The benefits of ridge
fumigation were not as great in a second
season as they were in the first season.
The trial area was heavily infested with
Verticillium wilt inoculum, confirmed by
the high level of disease that developed in
u n t r e a t e d plots and the presence of
Verticillium dahliae in these plants (Tate,
Cheah, 1983).
126
Application of metam sodium
Metam sodium is applied via t h e
sprinkler irrigation systems to control
Verticillium dahliae and other soilborne
pathogens. The effectiveness of metam
sodium in a trial in Israel for control of
Verticillium throughout the top 40 cm soil
l a y e r w a s i n f l u e n c e d by mode of
application of the chemical (concentrate
vs. dilute); type of soil, soil moisture, and
the rate of water application. When applied
DR. ALBERT
to soils with medium or high clay content
in the concentrated mode (dissolved in
the first 10% of the irrigation water), the
chemical killed Verticillium throughout a
deeper soil profile than by dilute application (dissolved in the whole irrigation
volume) especially in poorly structured
soil in which water percolation is slow. In
a clay soil (54% clay) with well defined
aggregarated structure which enables
quick water percolation, metam sodium
O.
PAULUS
applied in a dilute mode killed Verticillium
to a deeper layer than in a loessial soil
(20% clay) with a single grained structure
(slow water percolation). When metam
sodium was applied in a concentrated
mode, it was found to be important to
irrigate a dry soil at a low rate of water
application, in order to obtain uniform
control throughout the treated soil profile
(Ben-Yephet, Frank, 1989).
127
Diseases and soil solutions
References
BEN-YEPHET, Y . a n d
FRANK, A . R .
1989.
Factors affecting the efficiency of
metham-sodium in controlling Verticillium dahliae. Acta Horticulturae
255:227-232.
T. A. 1989.
Useofsoilsterilantsin
Florida vegetable production. Acta
Horticulturae 255:61-72.
BEWICK,
R. N . , et. al. 1 9 8 2 . Corky root of
tomato in California
caused by
Pyrenochaeta lycopersici and control
by soil fumigation.
Plant Disease
CAMPBELL,
66:657-661.
D. C. 1989. Control of verticillium
wilt of strawberry
in Britain by
chem ical soil disinfestation. Jour. Hort.
Sei. 64:683-686.
HARRIS,
et. al. 1 9 6 2 . Soil fumigation
found essential for maximum strawberry yields in southern California.
Calif. Agric. 1 6 : 4 - 6 .
JOHNSON, H . ,
JONES, J .
P.
and
OVERMAN, A . J .
1985.
Management of Fusarium wilt, Fusarium crown rot, Verticillium wilt (race
2), southern blight, and root-knot of
tomato on fine sandy soils. Proc. Fla.
State. Hort. Soc. 9 8 : 2 2 9 - 2 3 1 .
A. J . and J O N E S , J . P. 1984. Soil
fumigants for control of nematodes,
Fusarium wilt, and Fusarium crown
rot of tomato. Proc. Fla. State Hort.
Soc. 97:194-197.
OVERMAN,
TALBOYS, P . W . , W A Y , D . W . a n d BENNETT,
M. 1966. Comparison of chloropicrin
and metham sodium as pre-planting
soil treatments for strawberry wilt
(Verticillium dahliae Kleb) control.
Plant Pathology 15:49-55.
and C H E A H , L . H . 1983. Ridge
fumigation for control of Verticillium
wilt in strawberries. Proc. 36th N. Z.
Weed and Pest Control Conf. 79-82.
TATE, K . G .
A. 1979. Fumigation against
fungi. In Soil Disinfestation, Elsevier
Scientific Publishing Company, p. 163183.
VANACHTER,
et. al. 1 9 7 4 . Preplant soil
fumigation
with methyl
bromidechloropicrin mixtures for control of soilborne diseases of strawberries.
A
summary of fifteen years of development. Agric. and Environment, Elsevier Sei. Pub. Company, 2 2 7 - 2 3 6 .
WILHELM, S . ,
et. al. 1 9 6 1 . Verticillium wilt
of strawberry controlled by fumigation
with chloropicrin and chloropicrinmethyl bromide mixtures. Phytopathology 5 1 : 7 4 4 - 7 4 8 .
WILHELM, S . ,
M U N N E C K E , D . E . a n d VAN GUNDY, S .
D.
1979. Movement of fumigants in soil,
dosage responses, and differential effects.
Ann. Rev. Phytopathol. 17:405-429.
128
DR. ALBERT
Dr. Albert O. Paulus has been a member
of the Plant Pathology Department,
University of California, Riverside,
California from 1954 to the present time.
Obtained PhD in Plant Pathology from
the University of Wisconsin, Madison,
Wisconsin in 1954. Investigated diseases
of vegetable, small fruit, ornamental and
field crops and their control. Worked with
Professor Wilhelm, Harold Lembright, and
Richard Storkan in developing pre-plant
soil fumigation for the control of plant
pests. Named fellow of the American
O.
PAULUS
Phytopathological Society in 1981.
President, Pacific Division, American
Phytopathological Society, 1986-1987.
Keynote speaker at XIV Strawberry
Symposium, Congreso Asociación
International, Norcofel, Spain, 1988.
P r e s e n t e d l e c t u r e s at Q u e e n s l a n d
Agricultural College, Lawes, Australia,
1984. Research and extension leader on
cucurbit diseases, USAID project between
Egyptian and University of California
scientists, 1982-1983.
129
Solarization
in México
D R . FLORENCIO JIMÉNEZ DÍAZ
INIFAP
DR.
Introduction
S o i l solarization is a technique which
offers very promising chemical-free
alternatives for controlling plant diseases
caused by soil-borne microorganisms.
Solarization is a term describing a technique which consists in trapping solar
energy with clear polyethylene. Captured
heat acts as a lethal agent which reduces
soil-borne pathogen inoculation. Among
the characteristics clear polyethylene has
to offer are: its relatively low cost, excellent
chemical resistance, hardness and flexibility; it's free of toxic substances and
odors, and has low permeability to water
condensation. These features are used to
trap solar energy more efficiently. The
main purpose of the following document is
to show results reported all over the world,
and those obtained in Mexico proving that
this method offers effective soil-borne
pathogen control, thus increasing yield
and quality of the crops, besides prolonging
the use of land available for agricultural
production.
Traditional ways of using heat
to control disease
Heat has been used to control plant
diseases for years. The main variants
FLORENCIO
JIMÉNEZ
DÍAZ
reported are steam and hot water applied
directly to the soil or vegetable material.
An important bibliographical revision
on the methods for soil disinfection with
steam was carried out in 1955. The study
pointed out the effectiveness of this method
in eliminating all soil microorganisms
(fungi, bacteria, actinomycetes, nematodes, etcetera) through overexposure to
high temperatures. 46
Commercial m e t h o d s for soil
sterilization with s t e a m have been
described. This method requires 1802F
temperatures at a constant rate during
thirty minutes. 2
There is another soil treatment using
steam and air and requiring lower temperatures which has the advantage of being
selective in its extermination of plant
pathogens, without destroying pathogen
antagonists such as bacteria and actinomycetes. This has avoided recontamination risks when inducing an adequate
biological control with the help of soilborne non-pathogenic microorganisms.5'49
There have been reports 3,7 - 33 ' 41,42,48
from several crops of the use of heat applied
directly to vegetable tissue to obtain
virus-free material. Other studies
establish the elimination of bacteria, 17
micro-plasms, 36 nematodes, 16 and some
other microorganisms through heat.
133
Solarization
in México
Use of plastics for plant
disease control
A reduction in the incidence of cabbage
hernia has been associated with an
increase in soil temperature due to solar
radiation in a field covered with polyethylene. 69
Peanuts sown after a solarization period
of six weeks resulted in a significant
reduction of plants infected with Sclerotium rolfsii and weeds, together with a
52.8% and 123.5% increase in total yield
and fruit quality, respectively. Plastic soil
heating reduced Aspergillus spp. colonization in pods.20
The use of clear .03 mm (30 pm) thick
polyethylene to cover a previously irrigated
plot during the months of July through
August has been consigned. In this study
Verticillium dahliae was eliminated to a
depth of 0-25 cm after two weeks of
treatment. 34
Fusarium oxysporum f. sp. lycopersici
populations were reduced 94 to 100% at a
depth of 5 cm; 68 to 100% at a depth of 15
cm; and 54 to 63%, 25 cm below. Maximum
temperatures on treated soils fluctuated
between 49 and 52s C at a depth of 5 cm;
reaching42 s C at 15 cm. Field experiments
with eggplant and tomato reported a
reduction in Verticillium, which fluctuated
between 25 and 95%. Besides weeds were
controlled and plant growth and yield were
improved.
In cases where there were temperature
increases from 36 to 48SC in the top 5 cm
of moist soil covered with polyethylene,
the temperature ran between 44 and 522C
on dry soil to the same depth. The
temperature increased from 32 to 38SC, 4
to 20 cm deep on moist soil and from 35 to
392C on dry soil. Sclerotia from artificially
inoculated Sclerotium oryzae last between
95-100% of their viability.24
134
The effectiveness of solar soil heating
with clear polyethylene for controlling
fung; in onion crops was also proved. Solar
heating reduced the incidence and severity
of pink rot caused by
Pyrenochaeta
terrestris 73-100% during the seven months
following treatment, when the plants were
growing. Rhizoctonia solani and Fusarium
infections as well as weeds were also
considerably reduced. 35
Excellent control of the Ditylenchus
dipsaci nematode in garlic crops was
achieved by covering the plot with clear
polyethylene. Results were similar to those
obtained with methyl bromide. 57
The effect of covering soil with clear
polyethylene in the viability of plant pathogens was determined in an experiment
with: Fusarium oxysporum, Pythium irregulare, Plasmodiophora brassicae, Sclerotium cepivorum, S. rolfsii, Sclerotinia
minor, Verticillium dahliae and the Macropostonia xenoplax, Meloidogyne javanica,
Pratylenchus penetrans and Tylenchulus
semipenetrans nematodes. Preliminary
tests showed that the pathogens died at
temperatures within the 38 to 552C range.
The most sensitive to the treatment were
nematodes and V. dahliae, S. cepivorum
andS. minor fungi, while F. oxysporum, P.
irregulare and P. brassicae were the least
sensitive. 51
Studies were carried out to determine
the efficiency of soil solarization with clear
polyethylene to control
Verticillium
dahliae and Pratylenchus thornei. The soil
was irrigated and covered with 0.04 mm
polyethylene for 31 days, during which it
was kept moist. Potatoes were then planted
on this treated soil. Solarization eliminated
V. dahliaemicrosclerotia, reducing disease
incidence 96 to 99%, and the P. thorrei
population diminished 80-100%, weeds
were also controlled, increasing yield 35%
in contrast to the witness. 19
DR.
The soil was covered with clear polyethylene to determine pathogen control.
During the treatment the plot was irrigated
with 5 to 10 cm of water. Temperatures
were consistently higher in plastic covered
soils than in uncovered ones and were
lethal to many fungi. Rhizoctonia solani
was eliminated from the 15 cm top layer of
the soil after two weeks of treatment.
Verticillium dahliae, Pythium spp. and
Thielaviopsis basicola were essentially
eradicated up to a depth of 46 cm covered
during four weeks. 52 ' 53
An experiment in which moist soil was
covered with clear polyethylene for a four
and a half week period during the summer
to evaluate the behavior of phytopathogens
at high soil temperatures, found that
populations of Agrobacterium, Pseudomonas, Gram positive bacteria and fungi
were immediately reduced after treatment
and remained significantly low after six
and twelve months. 58
The effect of solarization
on soil bacteria
Four to five week solarization treatments applied during the summer reduced
Agrobacterium species populations; an
effect which lasted up to twelve months.
In another experiment it was established
that the percentage of Gram positive bacteria colonies exhibiting in vitro antibiosis
against Geotrichum candidum increased
close to twenty times more in solarized soil
as compared to the witness. 58 60
The effect of solarization
on phytoparasitical nematodes
Total nematode populations of Pratylenchus protensis, Rotylenchus incultus,
Criconemella xenoplas and mixed populations of Paratrichodorus lobatus plus P.
FLORENCIO
JIMÉNEZ
DÍAZ
minor-were reduced between 37 and 100%
of their original levels through soil solarization. 6
When d e t e r m i n i n g t h e effect of
solarization on Macroposthonia xenoplax,
meloidogyne javanica,
Pratylenchus
penetrans and Tylenchulus semipenetrans
nematodes it was found that these were
more susceptible than common soil fungi
under the conditions of this experiment. 5
Nematode control with soil solarization
was compared with chemical control.
Excellent results were obtained with clear
plastic placed before planting. Chemical
products initially reduced populations,
which then increased considerably by the
end of the crop.57
Field experiments for 4-6 weeks with
solarization and/or nematocides, reported
that with solarization and solarization +
nematocide, reductions between 42-100%
were achieved in t h e
Meloidogyne,
Heterodera, Pratylenchus,
Paratrichodorus, Criconemella, Xiphinema
and
Paratylenchus populations in contrast to
the witness. When only the nematocide
was used, reductions were significantly
lower.59
Effect of soil solarization
on weed control
Different solarization periods (from one
to four weeks) were tested as was their
effect on weed emergence. The841 grasses
found in the witness were reduced to 9 in
four week treatments. 300 other plants
were found in the witness which were
controlled 100% a f t e r 4 weeks of
solarization. Morning glory was reduced
from 76 in the witness to 2 in solarized
plots; 100% purslane was found, and
coquillo was unaffected by solarization.
An investigation to compare clear and
black polyethylene control over a series of
135
Solarization
in México
weeds found clear plastic offered better
control and residual effects of up to eleven
months. Different treatment periods were
also tested and determined that after 6
weeks purslane and morning glory were
eliminated 100% in counts carried out
after three and twelve months, respectively.30
Solarization treatments lasting 10,
20, 30, 40 and 50 days for weed control concluded that longer solarization
periods drastically reduced weed populations except in the case of fox tail. It
was also observed that previously irrigated soils were better controlled than dry
ones.43
Control of viral diseases
with plastics
Literature reports certain viruses
t r a n s m i t t e d by aphids which attack
cucurbitaceae in most producing parts of
the world. 21 ' 44 - 47 Such is the case of
watermelon mosaic virus 1 and 2, cucumber mosaic virus and squash yellow mosaic
virus. Plastics have been used to control
these diseases based upon the theory that
reflecting covers confuse and disorient
insects so they fly above and away from
the mulch, instead of landing on the plant
to feed.45
The effect of several colors of plastic
mulch was determined for the percentage
of squash showing symptoms of watermelon mosaic virus. The lowest percentage
of sympto-matic fruit was observed in white
plastic combined with oil.11
When testing different reflecting
materials in order to measure the degree
to which they repel vector insects (plant
lice), and so reduce virus incidence in
melons, the most outstanding treatment
proved to be a clear plastic cover over 70%
of the soil.43
136
Temperature and moisture changes
in plastic covered soils
When using 15 cm wide strips of
polyethylene to increase soil temperature
to a depth of 15 cm, it was observed that
heat was retained at night. Temperature
increases with black polyethylene were
lower, but heat retention at night was
higher. 63
Higher temperature increases have
been reported for clear plastic than for
black polyethylene. Soil moisture was
slightly higher in covered soil than in
uncovered soil.29
The effect of the width of the polyethylene strip on soil moisture retention
was observed. Results show that at least 6
inches have to be covered in order to achieve
a significant difference from the uncovered
witness. 24 inch strips were superior to 6
inch ones.37
A model to forecast temperatures in
polyethylene covered soils was developed.
Significant temperature increases were
proved in moist polyethylene covered soil.
This is due, in the first place, to the fact
t h a t evaporation is eliminated, and
partially due to the greenhouse effect of
the polyethylene cover. In the case of
covered dry soil, the greenhouse effect
dominates, thereby achieving a lower
temperature increase. It has also been
reported that heating on the edges of the
plastic strip is lower than through the
center, so a narrower strip is less efficient
(heat-wise) than a wider one.39,40
Maximum moisture deviations occur
in uncovered soils as opposed to polyethylene covered soils.32
Temperature increases of up to 10 to
12fiC in the top layers have been obtained
in soil covered with clear polyethylene, as
well as increased organic and mineral
compound concentrations. 12
DR.
Effect of temperatures
on the development and viability
of soil pathogens
Phymatotricum
omnivorum
grows
more rapidly at 28fiC. This fungus grows
and produces sclerotia at a range of 15 at
352C, but maximum sclerotia yield is
achieved at 282 C.38
Verticillium dahliae develops quicker
at 25 +- 12C under lab conditions, while
temperatures of 30 to 332C inhibit the
formation of microsclerotia. 8
Laboratory experiments determined
that temperatures between 37-502C were
lethal to the mycelium, spores and microsclerotia of this pathogen. An exposition
time of 28 days at 372C was considered the
lethal dosis for this fungus. 64
Species of the Fusarium fungus have
been recognized as warm climate. There
are reports that the disease caused by this
fungus progresses favorably under these
conditions. In a (PDA) cultivation medium,
the fungus grows at a rate of 9 at 37fiC.
Under natural conditions it grew better at
a rate of 24 at 312C. However, in the soil it
didn't grow at temperatures over 342C or
under 20SC.67,68
For some species of Phytopthora it has
been reported that conidia form at a 91%
relative humidity and is optimum at 100%,
at a temperature range between 3 to 262C,
the optimum being 18 to 222C. Optimum
temperature for zoospores is 122C, and
252C for the formation of the sporangium
germinative tubes. Zoospores germinate
faster between 12 to 152C.67
Soil temperature, humidity and ventilation affect the survival and movement of
most species of nematodes. It has been
determined that, in general, a temperature
of 202C and soil moisture content between
25 to 80% are f a v o r a b l e to t h e i r
development. 1,31
FLORENCIO
JIMÉNEZ
DÍAZ
Principles in soil treatment by heat
Soil treatment by heat is among the
oldest disease control methods, and has
proven effective to control a great amount
of pathogens. Nevertheless it's still underused. A list of principles on which soil
treatment by heat is based, follows:4
1. Tolerance to high temperatures
varies widely among living organisms.
2. Parasite microorganisms are more
likely to die at lower temperatures than
saprophytes.
3. Living matter is more prone to
destruction by heat at higher moisture
content in the soil.
4. The level of parasite propagule
dormancy is directly related to their
tolerance to heat.
5. The temperature required to kill a
microorganism is directly related to the
temperature range said organism has
adapted to during its development.
6. Damage to microorganisms through
h e a t t r e a t m e n t v a r y from delayed
germination to partial growth and eventual or immediate death.
7. Parasite microorganisms die at
temperatures only slightly damaging to
hosts.
Effect of soil solarization using clear
polyethylene on plant behavior
Field experiments have shown that
plant growth benefits from polyethylene
heating even in the absence of pathogens.
Tomato plantules placed on samples of
treated soil showed increased growth over
plantules growing on non-treated soil.12
In experiments to determine the effect of
solarization on soil nitrogen content,
maximum tomato yield (29.8% ton/ha) was
obtained with 60 kg/ha of N on treated
soil, whereas in non-treated soil maximum
137
Solarization
in México
yield (25.8 ton/ha) required 138 kg^ha of
N.32
Corn planted in soil previously treated
with clear polyethylene grew faster,
produced earlier and with higher yields
than plants cultivated on non-treated soil
or covered with black polyethylene. 29
Higher yields of garlic have been obtained
from soils treated with clear polyethylene
for pathogen control, than from those
treated with methyl bromide and ethylene
dibromide.57 Onion plant development
and yield increased between 109 and 125%
with clear polyethylene, with respect to
the untreated witness. 35
Peach bushes planted on solarized soil
showed a 25% increase in height and 42%
in fresh weight; increases in height and
fresh weight for Castile nut trees were 26
and 58%, respectively, when compared to
those grown on untreated soils.58
Highest pepper yields were achieved
from soils covered with clear and black
plastic as opposed to other techniques. 23
Also, radish, pepper and cabbage yields
were greater when cultivated on solarized
soil.61
Solarization increased pepper yield
20%, whereas when the same plastic was
painted and kept as mulch, yield was 53%
higher than the witness. In the case of
melon, a residual effect was detected on
138
yield when the fruit was planted the
following spring. 25
Solarization studies practiced
in Mexico
In the eighties, preliminary work
commenced in Mexico to determine the
feasibility of using solarization in some
areas of the country, where climate
conditions, economical importance of the
crops and complexity of phytopathological
problems indicated the possibility of
success. At the beginning of the investigation, the best solarization seasons were
defined, as was the best period for
solarization, its effect on soil pathogens
and on crop yields, as well as its
effectiveness in nematode and weed control.
At present there's information from
Irapuato, Apatzingan, Aguascalientes,
Sinaloa, Torreon, Tamaulipas, Sonora and
other places where problems caused by
Fusarium
spp, Rhizoctonia
solani,
Verticillium spp, Sclerotium cepivorum,
Phytopthora spp, virosis, nematodes and
weeds have been controlled in crops such
as strawberry, melon, garlic, tomato,
cotton, orchards, pepper, onion, watermelon, zucchini, cucumber, eggplant and
others (Table 1).
DR.
FLORENCIO
JIMÉNEZ
DÍAZ
Table 1
Place
Irapuato
Places and crops on which solarization research
has been carried out in Mexico
Problem
Crop
Strawberry
Apatzingán
Melon
Aguascalientes
Garlic
Sinaloa
Tomato
Torreón
Melon
Cotton
Orchards
Pepper
Onion
Watermelon
Zucchini
Various crops
(cucumber,
eggplant,
watermelon)
Tamaulipas
Sonora
Others
Fusarium, Rhizoctonia, Verticillium
Weeds, nematodes
Fusarium oxysporum f. sp melonis
Macrophomina phaseolina
Fusarium solani, virosis, weeds, nematodes
Sclerotium cepivorum
Weeds, nematodes
Fusarium oxysporum f. sp
radicilis Licopersici
Weeds, nematodes
Fusarium solani, Verticillium spp
Phymathotrichum omnivorum
Weeds, nematodes
Phytophtora, Rhizoctonia, virosis
Weeds
Nematodes
Weeds
Soil-borne fungis
Weeds
Nematodes
139
Solarization
in México
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fitoparásitos detectados en viñedos de
la Comarca Lagunera. Informe Anual
de Labores. CIAN-INIA-SARH. (En
proceso de publicación).
67
WALKER,
68
J. C. 1971. Fusarium wilt of
tomato. Monograph N2 6. The American
Phytopathological Society. 56 pp.
69
W H I T E , J . G . a n d BUCZACKI, S . T .
and
The effect of
petroleum mulch and polyethylene films
on soil temperature and plant growth.
American Society for Horticultural
Science. 8 5 : 5 3 2 - 5 4 0 .
WHITING,
66
1964.
D. 1982. La vid en México.
Datos Estadísticos. Colegio de Postgraduados. 321 pp.
i
TELIZ, O .
G. P. y Ruiz DE LA R. J. DE D.
1976. Comprobación de patogenicidad
VALLE,
VALLE,
J. C. 1969. Plant Pathology.
McGraw-Hill Book Company.
WALKER,
1979.
Observations on suppression of clubroot
by artificial or natural heating of soil.
Trans. Br. Mycol. Soc. 73(2). pp. 271-275.
Drip irrigation and
microspraying in
citrics and vines
B E N A M I BRAVDO
Agricultural Faculty
BEN AMI
Abstract
J 3 o t h drip and microsprinkler irrigation
a r e included in t h e category of
microirrigation namely, only part of the
soil and the root system are irrigated.
Methods consisting of partial wetting of
the root system require more frequent
water application since in this case the
soil serves as a water reservoir only to a
limited extent. Microirrigation methods
enable, however better control of the root
e n v i r o n m e n t with respect to water
availability, mineral concentration in the
root zone and aeration. Drip is a more
e x t r e m e form of microirrigation as
compared to microsprinklers, since the
irrigated soil volume in this case is smaller.
The use of soil tensiometers in drip systems
irrigated at constant frequent irrigations
enables to maintain a constant soil water
potential in the root zone and thereby
irrigate at the rate of consumptive use by
the trees. Results of irrigation experiments
BRAVDO
in citrus showed that root restriction,
created by the combination of one lateral
and high fertilizer concentration induced
a high rate of fruit bud differentiation and
consequently increased number of fruits
per tree. The increased fertilizer concentra-tion helped to prevent an overcropping
situation and the large number of fruits,
without reduction in fruit size, resulted in
a constant high production over the entire
four experimental years.
Drip is the dominant method of irrigation
in vineyards in the western world. The
combination of high water availability and
a e r a t i o n e n a b l e s to obtain high
productivity, large berry size and advanced
ripening. In winegrapes, the control of
vegetative growth at various stages of
fruit ripening is essential for improving
quality. Experimental evidences show that
correct use of drip fertigation enables such
a control and optimization of crop load, as
well as fruit composition relative to sugar,
acid and aroma compounds is obtained.
Intensification
and conduction
of tomato cultivation
D R . RODRIGUE N E L S O N VIGOUROUX
Agro Industrias Campus
DR.
^ ^ e g e t a b l e production in greenhouses
has increased in Mexico. These greenhouses are mostly dedicated to tomato
production, which is why I'd like to speak
about our experiences in this field.
A greenhouse is a work utensil which
must conform to a biological and economical framework. Some of the elements
determining its location are environmental
radioactivity, climate, water, soil and labor.
The quality of the plant in the greenhouse is very important, since production
depends upon it. It is precisely in the
greenhouse where the future of the crop
(and especially of the harvest) is prepared.
General aspects of plant production
a) A good plant is hard to define,
however its development must take into
account production goals and the biological
particularities of the crop.
1. Production goals
A well developed plant is that one
capable of producing the highest yield
with the best quality (shape, size, etc.).
This young plant is where the future of
the crop lies. As a matter of fact, it is
during this period when the formation of
RODRIGUE
NELSON
VIGOUROUX
cotyledons takes place, up until the
development of the second and third leaf
when the first blooming starts.
Light, temperature and nutrition are
the three elements that determine the
formation of the plantule. After the third
leaf to blooming, the environment must
not vary since a deficiency in any of the
elements (light, temperature, water and
nutrition) could result in flower abortion.
The quality of a plant can be judged by
certain visible characteristics, such as a
healthy appearance in all its parts,
turgescence and richness in dry matter,
smooth cotyledons. When transplanted, it
should be in a state such that will allow it
to withstand the environmental conditions. Plants should be homogeneous.
Plantules must be prepared in a greenhouse (we'll call it a multiplication greenhouse) dedicated to that purpose. A good
separation between stalks can be achieved
by allowing 20 pots per m2. The greenhouse must be equipped with movable
tables and adequate heating, independent
from external climate conditions.
Seed
It is advisable to submit perfectly
healthy seeds to thermo-therapy; a 60 s C
treatment results in disinfected seeds.
151
and conduction
of tomato
cultivation
Cultivation m e d i u m
Fertilization
Seeds can be sown in a humid medium,
that is also parasite-free, poor in salts,
slightly acid, enriched with nutrient
solution, etcetera.
It is a good idea to cover seeds with 1 to
1.5 cm (about .5 in) of substratum during
germination. Air temperature of the
substratum is kept steady at 20s C.
The strongest plants are selected once
cotyledons are horizontally well developed,
in other words, 10 to 12 days after sowing.
Malformed plants are discarded. Its very
important that cotyledons are in good
shape since the young plant totally depends
upon them.
Transplant will take place when the
first blooming starts.
Excess nitrogen should be avoided in
plantules. It should also be noted that
their absorption of phosphoric acid is
inhibited by low temperatures combined
with lack of light. Potassium partially
compensates lack of light.
C h a r a c t e r i s t i c of s u b s t r a t u m
1. High water retention.
2. Well ventilated; i.e. porous.
3. Allows good root development since
its not hardened.
4. Healthy or parasite-free.
5. pHfi.
6. Does not contain excess nutrients.
7. Can be soaked with 2 kg of fertilizer
per m3, in order to enrich it with phosphorus and potassium.
Temperatures
The temperature of the substratum
has a bearing on the growth of the roots
as well as water and nutrients. Growth
is inhibited at temperatures under 142 C;
while phosphorus absorption decreases
50% at temperatures between 18 and
12° C.
During the preparation phase of the
plant, temperatures act directly upon final yield in fruit size.
152
1. T r i m m i n g of s e c o n d a r y s t e m s
Typically, t h e main stem of an
indeterminate variety reveals shoots three
leaves before producing flowers (or clusters
of flowers), followed by three leaves,
cluster... etcetera.
The axil of every leaf produces a shoot
which develops a secondary s t e m .
Trimming consists in eliminating these
shoots to give the plant a more ventilated
structure, concentrating its strength to
producing larger fruits.
a) T r i m m i n g to a guide:
All axillar shoots are either broken off
manually or cut off with a knife after
they've grown 5 to 10 cm. All secondary
shoots —but not the main s t e m - are
eliminated.
Among the advantages of conducting
to a guide are:
- greater production precocity,
- higher production,
- larger size, and
- greater homogeneity.
2. T e r m i n a l t r i m m i n g
Indeterminate varieties of tomatoes can
continue growing indeterminately.
Depending upon the type of crop and
environmental conditions, a decrease in
the size of the fruits can be observed in the
higher branches, after the sixth, seventh
DR.
or eighth cluster.
In certain cases, and depending upon
desired results, the top of the plant (the
terminal shoot) can be eliminated; a
procedure which stems growth.
Trimming the plant to 6-7-8 clusters
(on the same stem) results in:
- fruits plumping out more rapidly,
- reaching maturity sooner,
- greater caliber (size and quality), and
- reduced cultivation period.
The cluster forms a thorn. If more fruits
occur in a bifurcated cluster, it's because
floral induction has taken place under
stress: cold, salinity, etcetera.
The terminal flowers of a cluster can be
eliminated to favor plumper fruits, leaving
for example, only five fruits to mature
identically to the same seize.
4. Eliminating leaves
Leaves aren't to be eliminated until
they're exhausted. A symptom of this is
that they become white (loss of magnesium) and brittle (easily crushed).
Anyway, these leaves should appear
under the cluster being harvested. If
symptoms of exhaustion show up in the
upper leaves, this means that there is a
nutrition problem.
It should be noted that fruits nourish
themselves from the reserves of the leaves.
An indiscriminate elimination of these
results in accelerated maturity, decreased
size, and loss of color.
RODRIGUE
NELSON
VIGOUROUX
soil and the quality of irrigation water.
The following information is a mere guide
and should be adapted to each separate
case.
In general it's important to keep
conductivity in the irrigation water after
adding the fertilizer. A good rule of the
thumb is not to exceed 1 gram of fertilizer
for every liter of water irrigated.
Fertilizers which leave saline residues
in the soil (sulfates, chlorides, etcetera)
must be avoided.
Its not advisable to supply Mg with P or
with the K, since this can result in
precipitations or interferences.
1. Fertilization balances
a) Seed beds and post-planting; until
the second cluster:
N-P-K;
15-30-15
b) From third cluster until the start of
harvest:
N-P-K
15-15-30
c) From the start of harvest until the
trimming of the plant:
N-P-K
15-10-30
d) From the trimming to the end of
harvest:
N-P-K
20-0-30
Magnesium is supplied separately from
the other fertilizers, preferably in the form
of magnesium nitrate (or as magnesium)
at a rate of one part for every five parts of
the potassium supplied.
2. Irrigation
III. Fertilizers
Instructions as far as balancing the
fertilizers to be used and watering the
plants are relative and provided only as
guidelines. The amounts to be supplied
depend upon atmospheric conditions,
observations of plant responses, type of
Irrigation varies greatly according to
the cycle of the crop:
a) Greenhouse sowing/Spring for
spring/summer harvest.
b) Summer sowing for fall/winter
harvest.
The maximum supply necessary in a
153
crop where the harvest and fructification
phases are to take place in mid-summer
would be 1-2 liters of water per plant a
day, at that moment.
V. How to increase the size
of the fruit
Some practices promote greater fruit
size:
- Using water with a low salinity level.
- Forcing nitrogenous fertilizer; a N/K
ratio of 1/1.5 or 1/2 during the plumping
phase affords interesting results.
- Trimming to a guide.
- Trimming after the sixth or seventh
cluster.
- Trimming the cluster to leave a
limited amount of fruits.
VI. Training
Due to the cultivation period, training
is particularly recommended for indeterminate type tomatoes. Training helps keep
the plant straight and well ventilated; it
sustains the weight during the long
production and harvesting period benefiting the quality of the fruit.
Traditional supports or trainers can be
easily modified with higher trainers (1.5
m to 1.8 m) to maximize yields from an
indeterminate plant.
When plants are fixed to a guide, the
number of plants can increase to 25
thousand per hectare.
Depending upon the composition and
structure of the land, a single central drip
line is used; in parcels with a high degree
of filtration a drip line in every plantation
row is used.
Carbon dioxide C0 2
The idea of applying CO., is to increase
154
its concentration thus stimulating better
plant development, increase in yield, better
harvest quality and earlier blooming and
fruit growth.
In most cases of indoor crops, atmospheric concentrations of CO, have always
limited p l a n t growth, since t h e s e
atmospheric concentrations can sometimes
decrease to levels below 180 ppm, while
normal levels rem between 300 to 350 ppm.
Benefits of applying CO,
- Pure C0 2 (99.5%) is available. Its use
avoids burning fuels which produce toxic
gases noxious to plants, such as sulphur
(S) by-products, nitrogen oxides (NOx),
and others.
- Profit increases exceed several times
the cost of the treatment and initial
investment.
- E q u i p m e n t for controlling and
calculating CO, concentrations is simple
and reasonably priced.
- Besides it has been proven that
modern techniques, such as the use of
plastics in agriculture, drip irrigation, soil
mulching, microtunnels and greenhouses
allow direct application of C0 2 on leaves.
- C0 2 prolongs tissue life.
- It also prolongs the productive life of
the plant, thus avoiding excessive tilling;
saving great amounts of plastic, drip
tapes, etcetera, and labor which, translates
into lower costs and greater profits.
CO., application technique is based on
the following:
1. CO, gas can be mixed with irrigation
water.
2. This mix is applied through the drip
irrigation system
3. C0 2 will spontaneously escape from
the soil into the atmosphere, a process
enhanced by changes in temperatures,
DR.
pH, etcetera.
4. C0 2 application becomes even more
adequate when drip irrigation is combined
with soil mulching.
RODRIGUE
NELSON
VIGOUROUX
5. Optimum applications are carried
out in greenhouses
6. C0 2 gas can be applied in the
irrigation hoses.
155
MEMORIAS
se terminó de imprimir el 18 de abril de 1994,
en los talleres fotolitográficos de Impre-Jal,
impresores de Guadalajara, Jalisco, México,
en Nicolás Romero 518.
La edición fue de 1,000 ejemplares,
y estuvo cuidada por el licenciado Alfonso Ñuño.

Organized by - Comité des Plastiques en Agriculture

Transcription

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