The Minnesota Flower Growers Bulletin

Transcription

The Minnesota Flower
Growers Bulletin
January, 1991
Volume 40, Number 1
Caladium Production
by
Michael Evans, John Erwin, and Royal Heins
uv
%.-.-&.”
Scientific Name: Caladium bicolor (G.
x hortulanum), Qladium gicturatum
Season of
Production and
Markets: The caladium is sensitive to
Familv: Araceae
chilling which limits its use in the northern
landscape. Caladium tubers are forced as
either a pot crop for the spring market or
planted out of doors as a specimen plant in the
garden. In some cases, mass plantings of
caladiums may be seen in more extensively
landscaped settings.
Oriain and Sites of Production:
The caladium is native to Peru and the Amazon
River District of Brazil. The majority of the
world tuber supply is produced in south
central Florida.
Selected
Species
CUltiVarS: C a l a d i u m g ictur-
An at 0 m v : The underground storage
and
has
lancelate leaves, is shorter and tolerates full
sun better than 5;. b i c o l o r . C a l a d i u m
g i c t u r a t u rn cultivars are usually
recommended for use in hanging baskets.
Colors on all cultivars tend to be darker when
plants are grown in the shade compared to in
full sun.
structure of the caladium is classified as a
tuber. A tuber is a modified stem structure
which develops below ground which is used to
store reserve carbohydrates. The Irish potato
is a tuber. Shoots develop from vegetative
buds (eyes) on the tuber. Caladium bicolor
has nearly heart-shaped leaves while G
gicturatum has lancelate leaves. Leaf colors
include green, white, red, and pink. Various
leaf coloration patterns exist among different
caladiurn cuItivars.
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Minnesota Flower Growers Bulletin
-
Volume 40, Number 1
January, 1991
Selected Species and Cultivars
Description
Cultivar
Color
Aaron
White
White heart-shaped leaf changing to light green and dark green at
leaf margins. White midribs extend to the leaf borders.
Candidum
white
white heart-shaped leaves with green midrib.
Candidum Junior
White
white heart-shaped leaves with green midribs. Shorter than
'Candidum'.
Carolyn Whorton
Pink
Light pink with darker pink veins and irregular green border.
Crimson Wave
Red
Crimson with green border.
Dr.Grover
Pink
Transparent pink with dark green border and red veins.
Fannie Munson
Pink
Bright pink with darker veins. May turn green with maturity.
Good in sun.
Fire Chief
Red
Crimson with green border and green spots.
Florida Cardinal
Red
Red with wide green margins.
Freida Hample
Red
Dark red with green border. Dwarf and good in sun.
Ithacapus
Red
Deep red with bright red spots.
June Bride
white
White to nearly translucent heart-shaped leaves. Narrow green
margins.
Lord Derby
Pink
Nearly translucent pink with green midrib and border.
Miss Muffet
Mixed
White with slight light green border and spots.
Mrs. Arno Hehrling
Pink
White with pink spots and dark red midrib.
Mrs. F.M. Joyner
White
White heart-shaped leaves with a pink hue. Red midrib.
Pink Beauty
Pink
Pink leaves with green border.
Poecile Anglais
Red
Centers of crimson with metallic green margin. Leaves are waxy
and undulated.
Postman Joyner
Red
Deep red with bright red spots.
Red Flash
Mixed
Red with irregular green border and white spots.
Rose Bud
Pink
Dark pink with irregular green border. Pink midribs extend
through green border to leaf margin.
Texas Beauty
Red
Dark rose with red midrib.
White Christmas
White
White heart-shaped leaf with prominant green midribs.
White Queen
Mixed
White with narrow green border and red midribs.
2
Minnesota Flower Growers Bulletin - January, 1991
Environmental Requirements:
Light: Although each cultivar has its own
optimum light level, most cultivars perform
best at approximately 5,000 footcandles
(1,000 micro mol s-1 m-2) or in 60% shade
in Florida (Conover and Poole, 1973). The
'Holland Bulb Forcer's Guide' recommends
that caladiums should be grown at 3,0004,000 footcandles.
Insufficient light results in smaller
leaves, reduced plant height, and reduced
plant quality.
Excessive light results in
reduced coloration due to increased
chlorophyll (green pigment) production.
Plants may also be stunted and have smaller
leaves.
Temperature: Tubers should be stored after
harvest (cured) to promote rapid sprouting
after planting (see propagation). 'Curing'
involves exposing tubers to 9OoF for3 days
then storing tubers at 70-75oF for at least 6
weeks for early forced caladiums or storing
tubers at 70-750 F constant temperatures for
caladiums forced later in the season.
Most pot plant producers receive tubers
that already have been cured by the tuber
producer. If tubers are not to be planted
immediately, they may be stored. Generally,
temperatures of 70 - 80oF (21 - 27oC) are
recommended for storage. Relative humidity
should be maintained at approximately 75%.
Good air circulation should be maintained to
prevent build up of undesirable gases and to
prevent fugal growth on tubers. A fungicide
dust may also be applied to prevent fungal
growth on the tubers. Tubers should never be
stored below 70oF (21oC).
Optimal forcing temperature for
caladium
is
75-800 F
(24-270 C).
Temperatures can be raised to as high as 9OoF
(32oC) to increase the rate of leaf emergence.
However, forcing at 9OoF (32oC) or higher
temperatures reduces root growth. Bottom
heat is often beneficial to encourage
sprouting.
When caladium are in a
greenhouse with plants which prefer a cooler
temperature, cover pots with a clear plastic
to increase the pot temperature and relative
humidity under the plastic. After leaves have
emerged, temperature can be lowered to 70oF
(21 oC) without any detrimental effects on
plant growth.
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Volume 40, Number 1
When planting tubers out-of-doors,
tubers should be planted when the soil
temperature is 65OF (18oC) or above.
Water:
Plants should be watered when
medium begins to dry. Do not overwater as
root and tuber rot will occur.
However,
plants should not be allowed to wilt as
irreversible damage may occur. Tubers may
become dormant if the medium becomes dry.
F e r t i l i z a t i o n : Many types o f
fertilizers are acceptable. Conover and Poole
(1975) recommended 6 kg Osmocote (14-1414) per cubic meter of medium (6 ozkubic
ft) or 1 tsp per inch (15 cm) pot diameter.
A constant feed of 100 - 200 ppm nitrogen
and potassium weekly has also been used to
successfully grow caladium. Superphosphate
may be added prior to potting. The pH should
Dolomitic lime
be maintained at 5.5 - 6.5.
may be added to the mix prior to potting to
raise the pH if necessary.
Excess nitrogen may cause undesirable
green leaves (due to over production of
chlorophyll).
Gases: - A high relative humidity (75%)
is required during storage to reduce tuber
weight loss. No information is available on
the affect of C02 on caladium growth.
PrODCiaatiOn - Caladium propagation is
accomplished by tuber multiplication, tissue
culture or by seed. Tubers are the most
common means of caladium propagation.
Tuber propagation is usually conducted in the
spring. Pieces of tuber (1 cubic inch) with at
least 1 bud are planted in the field in spring.
Before planting tuber pieces are soaked in hot
water (122oF) for 30 minutes.
Plants
mature and tubers are harvested in August.
The tubers are placed in open containers for
drying and then placed in a forced air building
for curing (70 - 80oF, 75% RH). Curing
results in more rapid sprouting.
After
curing, tubers are dipped in or dusted with a
fungicide.
Caladium tubers are graded by the
circumference of the tuber. Tuber grades and
the respective sizes are shown in Table 2.
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January, 1991
Volume 40, Number 1
Table 2. Caladium tuber grades and their
respective sizes.
However, production time is increased.
................................
Growth
Grade
Reaulators: Soaking tubers
in 2,000 ppm Ethephon for 2 hours improves
uniformity and increases shoot number.
Forcing time is unaffected by Ethephon soaks.
Size
.............................................
Super Mammoth
4.5 inches
11.5 crn or greater
Mammoth
4.5 - 3.5 inches
11.5 - 9.0 cm
Jumbo
3.5
9.0
#1
2.5-1.5 inches
6.5 4.0 cm
#2
1.5
4.0
- 2.5
- 6.5
Plantina tubers - Medium should be
well drained and high in organic matter. The
media pH should be maintained from 5.5-6.5.
Tubers should be planted 2 -3 cm (1 inch)
below the soil line. The number of tubers per
pot is determined by the pot size and the
desired final plant size. Usually 1 mammoth
or jumbo tuber, 3 #l's , or 4 -5 #2's are
planted per 6 inch pot. One #1 or 2 #2's are
also be planted per 4 inch pot. Caladiums can
also be started in flats and transplanted to
pots to reduce the space requirement during
production.
inches
cm
-
1.0 inches
2.0 cm
New crop tubers (harvested in August) are
usually available in December. However,
with proper storage, tubers can be available
virtually year round.
Tubers should be inspected upon receipt
for signs of chilling injury and/or physical
damage upon delivery
Tubers should be firm. Tubers exposed to
chilling temperatures are often rubbery to
the touch. When cut, the tuber should be free
of milky-white areas and brown streaks
which may indicate the presence of fungal
pathogens.
Shoot
SDacinq -Pots may initially be placed potto-pot. When plants become larger, pots
should be spaced far enough apart to allow
good air movement and little shading.
Suppo r t -Caladiums generally do not
require support.
Product ion Problems:
1) insects -Caladiums do not, in
general, have serious insect pest problems.
However, root aphids and mealy bugs may feed
on tubers during storage. Mites, aphids,
mealy bugs, white flies, red spider mites, and
lepidopterous larvae may feed on the leaves.
Deve Io D m e nt= Shoot
number is increased in any one of 3 ways:
pinching, cutting tubers into pieces, or
planting tuber upside-down.
2) Diseases - Tubers should
always be inspected upon receipt. Tubers
with discolored areas or chalky substances on
the surfaces should be discarded.
1) Pinching- As with other crops,
pinching is used to increase the number of
shoots on a plant. In the caladium, the main
bud, or eye, is the dominant bud. If this bud
is removed before tubers are planted
(referred to as scooping) additional axillary
shoots will develop.
2) Large tubers may be cut in pieces,
allowed to suberize, placed back together, and
planted.
3) Tubers may be planted upside
down. Besides causing an increase in the
number ,of shoots emerging, the shoots are
shorter, and the finished plant is fuller.
Tubers may be attacked by many pathogens
F u s a r i u m , R h i z o c t o n i a,
including
Schlerotium, and Erwinia. A warm fungicide
dip (50oC or 122oF) for 10 - 30 minutes
prior to potting helps to control fungal
pathogens. In addition, a regular preventative
fungicide drench is recommended on a monthly
basis.
Dasheen Mosaic Virus (DMV) has been
found in many 'Candidurn' cultivars. A DMV
infected plant may not show symptoms of
4
De Hertough, A. 1985. Holland Bulb Forcer's
Guide. International Flower-Bulb Centre,
The Netherlands. pp. 177-180.
infection but plant size may be reduced by as
much as 30-50%.
Many root knot nematodes have been found
in association with caladiums in Florida.
Symptoms include discolored, decayed, galled
or deformed roots and stunted growth. Control
has been achieved with hot water treatments
and nematocides.
3) p H
Harbaugh, B.K., F.J. Marausky, T.F. Price,
and D.J. Schuster. 1979.Guidelines for
forcing potted caladiums. Florida
Ornamsntal Growers Assoc iation Newslettet.
2(1).
-
Often in the upper midwest
we can have difficulties maintaining a lower
pH, i.e. 6.0. If pH should rise above 7.0
caladium growth can be reduced and foliage
discoloration can occur. Therefore, it is
essential to monitor your pH on a regular
basis. In all probability the water pH may
need to be modified with an acid to lower the
water pH prior to watering a crop.
Harbaugh, B.K. and B.O. Tjia. 1985. 1985.
Commercial forcing of caladiums. Florida
Cooperative Extension Service. Institute of
Food and Agricultural Sciences. Circular
621.
Harbaugh, Brent.
1986. Visual nutrient
deficiency symptoms in Caladium x
h o r t u l a n u m 'Birdsey'. 3. Amer. SOC,
Hort. Sc i, , 1 1 1 (2):248-253.
4)
Magnesium d e f i c i e n c y Magnesium deficiency can occur in caladium
when the media pH rises above 7.0 and/or
when plants do nof receive magnesium
through the fertilization regime.
It is
necessary to monitor pH regularly and apply
magnesium to a crop on a regular basis.
Apply 2 oz/lOO gallons magnesium sulfate
(epsom salts) in a constant liquid feed
program or 8 oz/lOO gallons as a single
Do not mix
application once a month.
magnesium sulfate and calcium nitrate
together, as they will react to form a
precipitate.
Further
Volume 40, Number 1
Hartmann, H.T., and D.E. Kester. 1975. Plant
propagation:
principles and practices.
Prentice-Hall, Inc., Englewood Cliffs, N.J.,
U.S.A. pp. 494-500.
Marousky, F.J. 1974. Influence of curing
and low temperature during storage on
subsequent sprouting of caladium
tubers.
Proc. Fla. State. Hort. Soc. a7:426-428.
References
Aimone, T. 1985. Culture Notes: Caladium.
G rowe rTalks 49(1 ):22,24.
Auman, C.W. 1977. Three years of caladium
research. North Ca rolina Flower
Growers Bulletin. 21 (2):3-5.
Conover, C.A. and R.T. Poole. 1973. Influence
of shade level and soil temperature on
forcing of caladium bicolor. Fla. State
Hort. SOC. Proc,, 86:369-372.
Conover, C.A. and R.T. Poole. 1975. Influence
of fertilizer level, apical. bud
removal, and tuber orientation on
forcing of Caladium bicolor.
HortScience 10:226-227.
5
Volume 40, Number 1
Caladium Production Schedule
i
85 -t
Drop Temperature
Plant
i
z
v)
Q)
J.
80 -
2
cr,
Q)
'CI
v
Q)
75
-
L
=I
Q
w
L
Q)
E
s
70 -
65
0
I
I
I
I
2
4
6
8
f
10
Time From Planting
Marousky, F.J. and J.C. Raulston. 1974. Wilfret, G.J., and B.K. Harbaugh. 1990.
Effect of chip spacing and nutrition
Influence of temperature and duration
on production of caladium tubers.
of curing, storage, shipping and
Flor. Orna. Grower Assoc.
forcing periods on caladium growth.
Newsletter, 135-9.
Proc. Fla. State Hort. SOL 86~363-
368.
Wilson,
Marousky, F.J. and B.K. Harbaugh. 1976.
Influence of relative humidity on
curing and growth of caladium
tubers. Proc. Fla. State. Hort. SOC,
891284-287.
6
M.R., and T.H. Nell.
1984.
Caladiums. Greenhouse m a n a u ,
2168-73.
Volume 40, Number 1
Producing Cut Flowers
-
Florist Statice
(reprinted from 'The Flower Market', 2(12):6-8)
Dr. William E. Healy, floriculture and ornamental horticulture specialist,
and lgnacio Espinosa, graduate student, Department of Horticulture, the
University of Maryland.
This article is one in a series "Enterprise
guide for Southern Maryland, providing
information about alternative agricultural
enterprises for growers. These trials were
conducted in Maryland, and some of the
information may have to be adjusted for the
climate where you are.
Choosing a Variety
A number of varieties of L. sinuaturn are
available, with most seed producers having
their own strains. The varieties range from
white (alba), to various shades of pink, blue
and deep purple -- see statice varieties table.
General Information
Annual statice cultivars ( L . sinuaturn)
originating from the Mediterranean region,
are becoming more popular in the U.S. Statice
is commonly used either dried or fresh as a
filler flower in arrangements. The multiple
uses of statice make it an ideal crop for
certain climatic areas. Growers can produce
statice for the fresh cut market and sell the
crop during the early spring.
STATICE VA RI ETIES
Variety
Fortress apricot
Fortress dark blue
Fortress heavenly blue
Fortress purple
Fortress rose
Fortress yellow
They also can harvest the drop and dry it for
winter sales. Optimum growth of statice
occurs during the cool seasons of the year
when most growers have time to devote to
production of this crop.
Blue river
Bondeuelli
Color
Pastel oranges
Dark blue
Light blue
Purple
Rose
Yellow
Deep blue
Bright
golden yellow
Kempf's blue imp.
Lavandin
Market grower's blue
Midnight
Surworowii (Rattail statice)
Statice may b e produced year round,
anywhere cool temperatures are found.
Planting statice in different climatic zones
influences time of flowering. In temperate
climates, it is generally grown as a summer
crop, while in tropical regions, statice is
grown in highland areas during the winter.
Dark blue
Clear lavender
Deep blue
Deep blue
Rose
Source: Fred Gloeckner Catalog, 1986.
Florist statice is an annual plant which as a
rosette plant habit. The plant has deeply lobed
leaves which grow parallel to the soil. The 12
to 24" flower stems have colored bracts
which surround the white flower. The bract
colors include white, yellow, lavender, peach
and shades of blue.
Producing the Crop: The total production
time from sowing to setting the plants in the
field is about 8-10 weeks. Use husked (or
decorticated) seeds whenever possible to
prevent fungal diseases.
Husked seeds
7
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January, 1991
Volume 40, Number 1
After transplanting, fertilize the plants to
simulate rapid growth. Add Osmocote 14-1414 to the soil at 8 pounds per cubic yard or
use 400 parts per million (ppm) weekly
liquid injection of 20-20-20 fertilizer.
Before planting in the field, broadcast
superphosphate at 500 pounds per acre, and
apply nitrogen at 30 pounds per acre over the
field and cultivate into the soil. Band either
500 to 600 pounds of nitrogen per acre of
Osmocote 18-6-12 on the center of the bed.
germinate quickly and uniformly and can be
sown easily. Broadcast the seeds over a tray
of potting soil and potting soil and cover
lightly. Use a sterile mixture such as 1:l:l
(by volume) of peat, sand, and vermiculite.
You can also successfully plant seeds by
machine into plug flats.
Keep the trays moist during germination,
which takes up to 7 days, at 25OC. The
germination rate is reduced at lower
temperatures.
After germination, reduce
irrigation to prevent damping off. Decrease
temperatures after germination to 20oC
during the day and lOoC at night.
Freely water statice after planting, and
keep the soil moist until 3 to 4 weeks before
harvest begins. After that, do not water until
the first harvest is complete, otherwise it is
very difficult to keep the humidity low, and
botrytis mold may develop. Once the first
harvest is complete, make a single application
of water if necessary.
Transplant the seedlings when the first
true leaves have fully expanded, usually 14 to
18 days after seeding. Transplanting before
true leaves have expanded reduces seedling
survival.
Seedlings can be grown in
individual pots, cell packs, or Speedling
trays.
Cont ro I I ing
During the last 4 weeks before field
planting, grow the plants at a temperature of
1OoC or below to encourage the plants to
mature and start budding. Consider the
likelihood of cool temperatures in the field to
determine the planting date. The earliest time
you should plant is late January, if you sowed
seeds in November. The last sowing should be
made at the beginning of March, although this
late sowing is not practical if the weather is
warm in April.
Pests:
Insects
APHIDS - Aphids can rapidly develop to the
point where chemical control is necessary.
Many species of insects attack statice, but
there are many other insects that could
seriously damage statice. (Contact Dr. Will
Healy for current chemical control
recommendations at 1-301-405-4356)
LEPIDOPTEROUS LARVAE - This insect group
includes armyworms, cutworms, and loopers.
These caterpillars usually attack the tender
terminal growth
Remember that cool temperatures and long
days (LD) promote flowering. Temperature
greatly affects growth, budding and flower
development. Stem elongation, leaf initiation,
and growth are promoted by high
temperatures while flower growth is
promoted by low temperatures.
SUCKING & RASPING INSECTS - This insect
group includes aphids, mealy bugs and thrips.
The damage these insects cause is minimal,
and large populations rarely appear.
MITES - Spider mites cause the most serious
damage to statice. They may appear in large
numbers on the underside of he leaves.
Populations of these insects usually peak
during flower harvest and large numbers
migrate from the leaves to the flower spike.
Fertilizing the Soil:
Based on the
differences between the location and time of
the year when statice is produced, it is
difficult to recommend a specific fertilizer
program.
Use dolomite or limestone to
maintain a pH level of 6.0 to 6.5. It is
important to avoid high salt levels in the soil,
since this reduces plant vigor to the point
where ,flower stem length is adversely
affected.
8
Volume 40, Number 1
stems, although the overall yield per unit
area may be reduced. The weaker growth
which results from close spacings requires
support, and a single layer of wire mesh is
commonly used.
Diseases
Foliage, flower and soil borne pathogens are
limiting factors in the field production of
quality statice.
The major foliage and flower diseases are
Anthracnose, Cercospora, and Botrytis.
Crown rots may be cause by Colletotrichum,
Rhizoctonia, and Southern blight (Sclerotium
rolfsii) .
Use a preventive maintenance spray program
which alternates combinations of fungicides,
insecticides, and acaricide every 10 to 14
days for statice, since spray on demand
practices are undeveloped. B
Botrytis is a problem with greenhouse grown
statice. It can attack at any time from the
propagation stage to flowering, and can cause
serious losses if it is allowed to become
established.
To maintain a clean crop,
co mbine water ing, heating and vent iI at ing
techniques to keep the atmospheric humidity
as low as possible at all times.
Harvesting the Crop
Cut the flower when 75% of the calyces show
color. Cut the stems with knives or scissors
as low as possible to the plant without
removing leaves. Dip the stems into a
bactericide solution (such as Constant at 200
ppm) immediately after harvest to prevent
stem decay and increase water uptake. Leaves
stems in warm (20oC) water overnight before
grading the stems into bunches.
Sellina The Flowers
Flowers are sold normally in 1 pound
bunches, which contain 7 to 16 stems
depending upon the variety. Yield may arrange
from 10,000 to 40,OO pounds per acre.
weeds
b
Oxidazon, EPTC, and DCPA are the most
acceptable herbicides for use in statice
production.
The use of EPTC requires
mechanical incorporation which limits its
usefulness for many planting procedures.
Considering this constraint, most statice
growers would be limited to Oxidazon or to
DCPA.
Plastic weed barriers can be
successfully used to control weeds.
Planting the Crop
Field Plant Spacing
Grow two to three rows of statice plants per
bed, and space the plants 12 to 14 inches
apart across the bed (alternate space), and 14
to 16 inches apart down the bed. The plant
density will be about 14,500 per acre with
beds on 54 inch centers.
Greenhouse Plant Spacing
For glazings with poor light transmission, or
for early production plantings, the density
should be one or fewer plants per square foot.
At this spacing, the plants will produce strong
9
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January, 1991
Volume 40. Number 1
Returns Per 10,000 Sauare Feed of Bed Area Planted
Market Price (Der bunch)
Bunch Number
$5.00
$4.00
$3.00
2,000
3,000
4,000
5,000
$10,000
15,000
20,000
25,000
$ 8,000
12,000
16,000
20,000
$ 6,000 $ 4,000
6,000
9,000
8,000
12,000
15,000 10,000
$2.00
.........................................
Trickle tube
Fertilizer pre and post plant
Mulching film and herbicide
Cover crop
Transplants
Planting labor (60 hour)
Harvest labor (700 hour)
Buckets
Bunching supplies
Floral preservative
$200.00
TOTAL
$9,072.00
$55.00
$500.00
$1 7.00
$2,500.00
$360 .OO
$4,200.00
$400.00
$600.00
$240.00
Statice is sold in 1 pound bunches which contain approximately 10 stems. The table indicates
the anticipated harvest income per 10,000 square feet of bed area planted. If stems are dried
and sold at a later date, the anticipated income may be higher. The number of salable bunches
may represent only 50% of the stems produced by the plants. Yield is significantly affected by
culhvar and planting date.
,
-
Volume 40, Number 1
January, 1991
Greenhouse Nutrition
by
John Erwin
Nutritional problems represent roughly
75% of the difficulties encountered in
greenhouses in the upper midwest.
Nutritional problems arise from over or
under application of nutrients, pH
modification of nutrient uptake, or
competition among nutrients for uptake. This
review is the first in a series of articles on
nutrition management in greenhouse crop
production. Each article will concentrate on a
given element which is important to plant
growth which we actively manipulate in
production. In addition, all of the articles
will tend to emphasize difficulties which may
arise in the management of a given element in
production using media with low cation
exchange capacity and generally high pH
conditions. Such conditions are prevalent in
upper midwest greenhouse production. The
first article will discuss the element
nitrogen.
Nitrogen
Nitrogen is a macronutrient. In other
words, it is a nutrient which is required in
relatively large amounts for plant growth to
occur. Nitrogen effects plant growth in a
variety of ways. The effects of high versus
low nitrogen nutrition is shown in the table
on page 14. Nitrogen is a component of amino
acids, proteins, vitamins, enzymes, and
alkaloids.
Primarily 2 forms of nitrogen fertilizer
are used in greenhouse crop nutrition:
nitrate and ammonium. The forms of nitrogen
vary in both their uptake and the ways in
which they are utilized in the plant. For
instance, most ammonium is directly
incorporated into organic compounds in the
roots. In contrast, nitrate forms of nitrogen
must be reduced to ammonia before being
incorporated into organic compounds and are
mobile in the xylem. Which form is best for
optimal plant growth is dependent on a
number of factors. This review will discuss
11
both forms of nitrogen which are used in
greenhouse crop production and how they
interact to affect plant growth.
Nitrate- Nitrate (NOS-) is an anion, i.e. it is
a negatively charged ion. Nitrate is actively
absorbed by plants. Absorption is generally
greater at low pH media compared to high pH
media. Uptake can be depressed by high levels
of ammonium in media surrounding roots
and/or high pH. Feeding with high levels of
nitrate will tend to increase the cation content
of plant tissues. In other words, levels of
calcium, magnesium and potassium tend to
increase whereas anion content will tend to
decrease. Nitrates must first be reduced
before they can be utilized for plant growth.
Bitrate reduction; As mentioned before,
nitrate must be reduced to ammonia before it
can be utilized for plant growth. The nitrogen
reduction pathway for higher plants is shown
below:
tQ-
+
8H+
+
86-
----
NH3
+
2H20
+
OH-
The reduction of nitrate reduction to
ammonia is controlled by 2 enzymes: nitrate
reductase and nitrite reductase. The activity
of these enzymes determines the availability
of nitrogen reduced from nitrates for plant
growth. The reduction of nitrate to ammonia
is an energy requiring reaction which
requires the presence of molybdenum.
Both roots and shoots are capable of
nitrogen reduction. A number of factors affect
where nitrate reduction occurs. The level of
total nitrate surrounding the roots is one
factor which determines the proportion of
nitrate reduction which occurs in the roots
versus the shoots. In general, when nitrate
levels are low, a high proportion of the
nitrate is reduced in the roots. In contrast,
when nitrate levels are high, a greater
proportion of nitrate is reduced in the shoots.
In part, this may be due to the energy
-
January, 1991
requirement for nitrate reduction.
Such
energy would be available for nitrate
reduction in shoots more readily that roots.
This would certainly be the case during the
day when carbohydrates are synthesized via
photosynthesis.
Plant species and age also affects where
nitrate reduction occurs.
Woody plant
species, i.e. trees and shrubs, reduce a
greater proportion of nitrates in the roots
compared to the shoots.
Conversely,
herbaceous species tend to reduce a greater
proportion of nitrates in the shoots. As a
plant ages, a greater proportion of nitrate is
reduced in the roots.
As eluded to earlier, the environment
affects nitrate reduction. Nitrate reduction is
diurnal, i.e. it does not occur continuously
during a dayhight cycle. Nitrate reduction
occurs primarily during the day and the rate
of reduction is proportional to light intensity.
The basis for diurnal reduction of nitrates is
presumably due to the energy requirement for
reduction
which
i s provided
by
photosynthesis.
In addition to carbohydrate availability,
the nitrate reduction is affected by the
availability of nitrate reductase. Nitrate
reductase is synthesized primarily during the
day.
Temperature has an effect on nitrate
reduction. Nitrate reduction increases as
temperature increases.
Ammonium- Ammonium utilization in plant
growth differs from that of nitrate in a
number of ways. Ammonium uptake occurs
optimally at neutral pH values. Absorption of
ammonium by roots tends to decrease the
plant tissue levels of a number of inorganic
cations such as calcium, magnesium, and
potassium while increasing the level of
inorganic anions such as phosphorus, sulfur,
and chlorine. Absorption of ammonium also
tends to decrease the pH of the surrounding
media. Ammonium cannot be stored in the
plant as nitrates can. Both ammonium and its
equilibrium partner, ammonia, are toxic to
plant growth at low concentrations.
Detoxification of ammonium and ammonia
occurs through incorporation of these
compounds into amino acids, amides, and
related compounds. Translocation of these
compounds then occurs in the xylem.
12
Volume 40, Number 1
A general reduction of growth and
eventually a damaging of plant tissue can
occur if ammonium levels in the media
become too high. Reduction of plant growth
and damage to plant tissues by high ammonium
is referred to as ammonium toxicity. The
exact basis for ammonium toxicity is not well
understood. However, ammonia toxicity may
occur due to a rapid permeation of ammonia
through biomembranes. Ammonia diffuses
rapidly across chloroplast membranes. Such
diffusion can be destructive to these tissues.
In addition, in media with a low cation
exchange capacity and pH values at or above
7.5 higher ammonium levels have been shown
to decrease both transpiration and
photosynthesis.
As with nitrate reduction, a number of
factors affect the rate of ammonium
incorporation within a plant. As with nitrate
reduction, ammonium incorporation requires
energy. However, the energy requirement for
ammonium incorporation into plant tissues is
less than that for nitrate reduction.
Ammonium incorporation into plant tissues
requires the presence of magnesium.
As with nitrate reduction ammonium
incorporation occurs primarily during the
day period. This is presumably due to the
energy requirement for this process.
Ammonium volatilization out of the soil can
occur.
Ammonium volatilization is the
release of ammonia out of the soil in a gaseous
form. Soil pH, calcium carbonate content,
cation exchange capacity, texture,
temperature, and moisture content all affect
the amount of ammonium volatilization.
Ammonium volatilization increases as pH
increases, calcium carbonate levels increase,
and temperature increase.
Which N Source to Use: The question arises
as to which form of nitrogen should be applied
to maximize desirable plant growth. Plant
growth often is best when both sources of
nitrogen are used in a fertilization program.
However, there are some crops which prefer
one source of nitrogen to another. For
example calcifuges, or plants adapted to acidic
soils, often have a preference for ammonium
forms of nitrogen. Examples of calcifuges in
horticulture includes azaleas, rhododendron,
and blueberries. In contrast, calcicoles, or
plants adapted to alkaline soils, often prefer
nitrate forms of nitrogen.
Examples of
-
January, 1991
calcicoles in horticulture include alpines such
as many species of gentians.
The media in which a crop is grown can
determine which source is most appropriate.
In soil based media or media which contain
high levels of vermiculite, ammonium levels
may tend to increase to undesirable levels.
The environment which plants are grown
under may greatly affect which form of
nitrogen is used for fertilization.
For
example, media temperature affects nitrogen
uptake and loss. The amount of ammonium
which is volatilized increases as media
temperature increases.
In contrast,
ammonium utilization by plants is generally
greater at low temperatures compared to
nitrates. Greater utilization of ammonium
relative to nitrates at low temperatures may
cause problems. We generally see an increase
in ammonium toxicity during periods of the
year when we tend to grow our crops cooler.
Greater ammonium uptake relative to nitrate
uptake in cool temperalure environments may
be one factor which contributes to ammonium
toxicity.
Availability of other minerals essential for
plant growth may determine which form of
nitrogen is best for fertilization. The uptake
of a number of desirable cations can be
limited by ammonium.
For instance,
potassium, magnesium, and calcium uptake
are all reduced in the presence of ammonium
forms of nitrogen. As a result applying
ammonium forms of nitrogen can aggravate
deficiencies of any of these cations. Nitrate
forms of nitrogen inhibit anion uptake such as
chloride. However, the amount of such anions
needed for growth is often not limited by
nitrates.
Interestingly, molybdenum
deficiencies are more prevalent on plants
which are fed ammonium compared to plants
fed nitrate forms of nitrogen.
At high pH levels ammonium uptake is
Crops are
preferred compared to nitrates.
often grown at pH levels greater than 6.5 in
the upper midwest due to the high water pH
and alkalinity.
Higher ammonium uptake
relative to nitrate uptake at high pH levels
may be another contributing factor to
ammonium toxicity which we may
occasionally see.
Root morphology is affected by the type of
nitrogen applied. In general, High ammonium
tends to decreased root elongation and increase
13
Volume 40, Number 1
lateral branching. To this end ammonium
forms of nitrogen may be detrimental to
survival of plants in an exterior planting bed.
Based on this information in this article,
the following recommendations can be made:
1) Application of ammonium to greenhouse
crops should be limited if a crop is grown cool, if
magnesium, calcium, potassium , or molybdenum
is limited, or if media pH is high.
2) Ammonium nutrition in the greenhouse may
be detrimental to survival of plants outside
following transplanting.
3) Ammonium levels tend to increase more
readily in media which are soil based and/or have
a high cation exchange capacity. Therefore if
such a media is used for crop production, soil
tests will need to be done regularly to closely
monitor ammonium levels.
4) High nitrogen levels early in development
and late in development may be detrimental in
crop production. High nitrogen levels early in
development tend to decreases rooting and
promote shoot growth. High nitrogen levels late
in development tend to decrease the postharvest
life of many of our crops.
Volume 40, Number 1
....................................................
High Chlorophyll conte
Decreased leaf area
Increased carbohydrate content
Decreased need for growth retardants
Increased postharvest life
Decreased water loss
ased need for growth retardants
Research Updat
John Erwin
The Effects Of Kinetin, STS,
and Sugar On Carnation
Post harvest Life
Researchers in Poland studied the effects of a
24 hour or constant application of kinetin (a
cytokinin), STS (silver thiosulfate), and/or
sucrose (table sugar) through the holding
solution on carnation postharvest life.
Materials were applied at the following rates:
kinetin (0.025 mM), STS (0.1 mM in 24
hour treatment and 0.2 mM in continuous
treatment, sugar (5000 ppm).
HQS
(8-hydroxyquinoline (0.65 mM)) was added
to any solution which contained sugar. They
found that:
14
1) A 24 hour treatment with either
kinetin or STS increased carnation
postharvest life (Table 1). Kinetin increased
postharvest life from 6.3 to 10.3 days. STS
increased postharvest life from 6.3 to 13.2
days. Addition of sugar to either kinetin or
STS did not increase postharvest life. When
STS and kinetin were combined, postharvest
life increased an additional 1.5 days.
2) When stems were treated for more than
24 hours, sugar had a pronounced effect on
flower longevity (Table 1). Sugar alone
increased flower longevity from 6.4 to 14.4
days. Flower longevity was greatest when
sugar, STS, and kinetin were added to the
holding solution.
-
Volume 40, Number 1
January, 1991
Table 1. The effect of kinetin, STS, and sugar
on carnation postharvest life.
Piskornik, Z. 1987. The effect of kinetin,
silver thiosulfate, and sucrose on the
longevity of cut carnations (Dianthus
caryophyllus L.) and ethylene production by
flowers. Experimental work of the institute
of pomology and floriculture, SkierniewicePoland, Series B. pp. 159-167.
is The Future Of Floriculture
Breeding In Biotechnology
have been limited to date. Part of the reason
for this is the strict monitoring and release
limitations imposed on the industry by federal
regulators.
Two molecular biology techniques are
increasingly useful in plant breeding: PCR
(polymerase chain reaction), and RFLP
(restriction fragment length polymorphism.
Of the 2, perhaps RFLP's will speed the
improvement of plants the most. Although
biotechnology may speed plant breeding in the
future, it will not outmode many of the
classical procedures of traditional plant
breeders.
Authors note: Commercial breeding programs
have made tremendous improvements in
floriculture. However, the dramatic move of
most universities from classical to molecular
methods for breeding may be somewhat
premature.
Abelson, P.
1990.
Hybrid corn. Science,
249:837.
Planting Date Affects Yield Of
Some Field Cut Flower Crops
Only?
Practical benefits from plant biotechnology
have not met the expectations we had a decade
ago. Perhaps the main reason for this is the
fact that the insertion of a gene or a few genes
may not necessarily produce a superior
variety of broad application. The successful
plant breeder must provide varieties and/or
hybrids which can withstand the great variety
of environments which we subject our plant
material to throughout the U.S.
An example of the tremendous
improvements which plant breeders have
been able to make over the years can be seen
in the corn industry. Corn yield is 5 times as
great per acre as it was in 1928. At least half
of that increase is due to new cultivars and
hvbrids. The other half is due to cultural
15
The effect of planting date on harvest date and
yield of a variety of field cut flowers was
studied at The University Of Georgia. Bulbous
tuberose
roots of liatrus (I iatrus spic-),
(Polianthes tube rosa), and Dutch iris (Jris x
hollandica) were planted between Nov. 1986
and Mar. 1987. Late planting extended the
harvest time resulted in higher yields longer
stems on liatrus and tuberose. The response
of iris was cultivar dependent. Late planting
of iris extended harvest time but decreased
yield for all Dutch iris cultivars except
'White Wedgwood'.
Yield and stem length were optimal 10-15
days after first harvest for liatrus, 4-5
weeks for single-flowered tuberose, and 5-6
weeks after harvest for double-flowered
tuberose. Tuberose stem length increased
over seasons regardless or cultivar.
-
January, 1991
Bonzai Can be used to Control
Growth Of Tibouchina and
Fuchsia Trees.
The effects of Bonzai on plant form and
pruning frequency on Tibouchina and fuchsia
trees was studied by researchers at The
University
of
British
Columbia
Paclobutrazol (Bonzai) treatments of 0,
0.125, 0.250,
and 0.500 mg/plant
eliminated the need for pruning during the
display season and improved the form of
Tibouchina. Paclobutrazol did not show any
benefit for fuchsia tree production. Trunk
calibre was reduced on both species on plants
which received a paclobutrazol treatment.
Roberts, C.M., G.W. Eaton, and F.M. Seyward.
1990. Production of Fuchsia and Tibouchina
standards
using
Paclobutrazol or
Chlormequat,
Hortsc ience ,25( 10):
1 2 4 2 - 1 243.
Calcium Nitrate May Reduce
Fluoride Injury
On Cut Roses.
Researchers at Washington State
University studied the potential for short
term treatment of cut roses with calcium
nitrate to reduce fluoride injury (Table 2).
Cut rose 'Samantha' were placed in deionized
water or a solution of deionized water
containing 20 mM calcium nitrate for 72
hours. Flowers were then placed in a solution
containing 0 or 4 mg fluoride/liter.
Fresh weight gain, solution uptake, flower
opening, and flower longevity were all
reduced by the presence of fluoride in the
holding solution.
Pulsing with calcium
nitrate improved fresh weight gain and flower
opening in solutions containing fluoride.
Flower longevity was increased in all
treatments which received a calcium nitrate
pulse.
Volume 40, Number 1
Table 2. The effect of calcium nitrate pulses
and/ or fluoride in a holding solution on cut
rose 'Samantha' flower opening and longevity.
Bud opening was on a scale from 1, a bud
slightly open at the apex, to 7, an open
flowers with stamens visible.
__-_________________-----------................................
Treatment
Opening
Longevity
(day S)
................................
Control Treatment
Pulse Alone
Fluoride Alone
Pulse Plus Fluoride
4.2
4.3
3.6
4.0
6.8
7.8
3.4
4.4
--__________--___---____________
Pearson-Mims, C.H., and V.I. Lohr. 1990.
Fluoride injury to cut 'Samantha' roses may
be reduced by pulsing with calcium nitrate.
Hortscience, 25(10):1270-1271.
Colchicine induced Polyploidy
May
Result in Superior Lisianthus
The effects of colchicine treatments on
lisianthus were studied at Beltsville
Agriculture Research Station. Applications of
1 drop of 0.05% colchicine on the apical
meristem daily for 0, 3, or 5 days. The 5
days treatment resulted in 1 tetraploid
lisianthus in 216 replicates. The tetraploid
lisianthus was shorter in height, had a
thicker calibre stem, and had similar flower
size compared to normal diploid plants.
Overall, the tetraploid had more desirable
characteristics than the diploid.
Griesbach, R.J. 1990. Colchicine-induced
polyploidy in Eustoma grandiflorum.
Hortscience, 25(10):1284-1286.
Increase Postharvest Life Of
Brodiaea
Researchers at the University Of
California studied the effects of various
compounds of the vase life of Brodiaea. The
typical vase life of an individual flower of
16
Volume 40, Number 1
Brodiaea is 4 days. Best vase life was
achieved by harvesting inflorescence 1 to 2
days before pollen shed of the first flower and
holding them in a solution containing 2%
sucrose and 200 ppm 8-hydroxyquinoline
(HQC). Display life was increased to 12 days
when inflorescence were treated in this
manner. Decreasing pH, pulsing with 10%
sucrose solutions, or addition of silver nitrate
did not increase vase life.
germination.
They found that seed
germination was greatest and most rapid
when:
Han, S.S., A.H. Halevy, and M.S. Reid. 1990.
Postharvest handling of
Brodiaea
flowers. $-lortscience, 25(10):1268-1270.
Roeber, R., B. Plenkers, and G. Ohmayer.
1990. Germination of Ranunculus-hybrids
( F l ) 'Bloomingdale' as influenced by
temperature
treatments. Abstract 1422
at ISHS conference in Italy.
Lighting Affects Rose Leaf
Appearance
Courtesy Of The U.S.
Cut rose growers commonly light their
crop using high pressure sodium lamps.
Researchers at the Research Station for
Floriculture in The Netherlands studied the
effect of supplemental lighting on rose leaf
morphology. They found that:
1)
Internode length of the 10
uppermost internodes was not affected by
supple mentat lighting.
1) Seeds were germinated under red light
as opposed to darkness.
2) Seeds were grown for 10 days at 43oF
followed by a temperature increase to 59OF.
Researchers in Tuscany are studying the life
cycle of the thrip. Apparently the thrip
* ) was introduced
(Frankliniella occ i d e n m
from the southwest region of the U.S. to
Holland in 1983. Since 1983, the thrip has
spread throughout Europe. Along with the
spread of thrips has come an increase in
tomato spotted wilt virus. A table of the
effects of temperatures of the various stages
of thrip development is shown below.
2) Leaves of lighted plants had less
leaflets. This was especially true of the
uppermost leaves.
3) Chlorophyll content was higher on
lighted plants.
4) Leaf weight was greater on plants
which received supplemental lighting.
Blacquiere, T., and G. van D. Berg. 1990.
Morphogenetic effects of
assimilation
lighting. Abstract 1781 presented at the ISHS
conference in Italy.
Temperature and Light Affect
Ranunculus Seed Germination
Researchers in Germany studied the effect
of light and temperature on ranunculus seed
17
Del Bene, G., and E. Gargani. 1990. Notes on
the biology of Frankliniella
gccidentlis
(Pergande) (Thys. Thripidae), a new pest for
greenhouse
crops in Tuscany. Abstract
2192 at the ISHS conference in Italy.
Biocontrol Of Soil-Borne Fungi
is in The Future
Researchers at the Hombolt-University in
Berlin are studying the use of various
bacterial antagonists for control of soil-borne
fungal diseases of vegetable and ornamental
plants produced in greenhouses. They found
that Bacillus subt ilis T 99 showed great
promise for controlling soil borne fungal
diseases especially in combination with low
doses of fungicides. Addition of Bacillus
subtilis T 99 was found to help control
Fusarium in carnation, 'Die-back' disease in
gerbera, corky root disease in tomato, and
Phomopsis root rot in cucumber.
Bochow, H. 1990. Biocontrol of soil-borne
fungal diseases in greenhouse crops. Abstract
2186 at ISHS conference in Italy.
Promalin
Increases
Break
Number In Bougainvillea
The effects of an application of Promalin or
G-benzyl-adenine (6BA) on Bougainvillea
branching and flowering was studied by
researchers at North Carolina Agricultural
and Technical State University. Plants were
potted and grown for 1 month. After 1 month
all plants were pinched and sprayed with
either 50, 100, or 200 ppm of promalin or
6BA to run-off. A second application of
growth regulator was made 1 month later.
Bougainvillea break and flower number
increased with application of either chemical
over all concentrations.
Flower number
increase was greatest with application of
benzyladenine. For example, flower number
increased from 25 flowers per plant on
untreated controls to 96 flowers per plant on
plants which received two 50 ppm
applications of 6BA 1 month apart. They
concluded that 2 applications of 6BA 1 month
apart at a concentration of 50 ppm will
significantly increase both break and flower
number in commercial Bougainvillea
production.
18
Volume 40, Number 1
Kamp-Glass, M., and M.A. Odgen. 1990. The
effects of 6-benzyl-adenine
and APromalin
(6-benzyl-adenine and 3-gibberellic acid)
on branching
and
flowering
of
Bouaa invillea a labra, Chois. Abstract 1955
at ISHS conference in Italy.
Bonzai Reduces By-Pass Shoots
In Azalea
Researchers at the University Of
California, Davis, compared the effects of
Bonzai and B-9 on azalea development. Azalea
'Rosaperle' was sprayed on September 30
with either 50 or 75 ppm Bonzai or 2500
ppm
B-9. Height retardation, effects on
..
flowering, by-pass shoot number and leaf
scorch were
among the treatments.
They found that:
1) Application of Bonzai 5-6 weeks before
low-t empe rat ure st or age (450 F) substituted
for the low light requirement to prevent leaf
drop during cooling on some cultivars.
2) Application of 50 ppm of Bonzai resulted
in moderate height retardation, earliest
flowering, no by-pass shoot development, and
no leaf scorch compared to other Bonzai and B9 applications.
Kofranek, A.M., and G- l-hson. 1990- The
influence O f triazole derivatives On the
reduction O f shoot Size and flowering O f
evergreen azaleas. Abstract 1945 at ISHS
conference in Italy.
Volume 40, Number 1
Water Management
The Key is Understancling Irrigation, Media and Fertilization
Dr. John A. Biernbaum
Michigan State University
The nutrient holding capacity of peat compared to soil
is a point that often confuses many students. It is
important to d
i that the values for CEC are often
expressed per unit of weight. This hides the fact that a pot
of peakvermiculite has about half the nutrient holding
capacity of a pot of soil. Peakvermiculite has seven times
the nutrient holding capacity of field soil per unit of
Current problems with water and fertilizer runoff or
percolation from greenhouses are the result of basic
cultural practices which have been used for over two
decades. Methods that made good sense in the mid 1960’s
when they were developed are no longer good enough.
Taking the time to understand the basis for our current
methods can help us to identify ways to deal with runoff.
weight. However, since the peat has such a low density,
when equal volumes are compared there is twice the
nutrient holding capacity in a pot of soil. This is an
important point when we consider what happened to
f e r tih tio n practices as soilless media were adopted.
Wakillgprpctices
Several important developments occurred during the
late 1950’s and early 1960’s that d r a m a t i d y idluenced
greenhouse production.
We often hear how the
development of plastic films changed greenhouse
structures. The development of plastics also lead to the
production of new imgation systems. Spaghetti tube drip
systems for pots and spray lines for beds made rapid
application of large volumes of water very easy.
With the new irrigation systems, watering required
less labor. There was also less grower control over the
volume of water applied. Some of the systems developed
did not make uniform applications of water. The lack of
uniformity of application was often compensated for by
watering until the driest spot was wet.
Development of totally automated imgation system
became a priority and the question of what was the best
way to schedule irrigations was addressed. Much like
today, media moisture content could be measured with a
tensiometer, plants could be put on a scale with built in
switches, or light levels could be monitored and used to
determine watering frequency. At that time, however, the
method chosen to automate irrigation was to water at a
regular time interval with time docks. This was the easiest
and most efficient method for the largest number of
growers.
N.biat-cI.uih
Field
soil
CEC meq/100gm
grsm/enbican
eabicdpot
4 m
F
20
13
U50
325
Peat:
Vermic
141
0.1
1250
176
‘.
At the same time our currenf watering and media
recommendations were developed, it was determined that
frequent applications of water soluble nutrients were
needed to compensate for the high volumes of water
applied and the low CEC of the mot media. High levels of
fertiiizer were needed to maintain a n adequate level of
fertility. Frequent applications of fertilizer were also due
to the increasing use of fertilizer iqiectors and water
soluble fertilizers. Fertilization was easy, as it should be,
but this lead to u n n v applications.
Growers were taught to apply fertilizer and water in
excess of container capacity to reduce the potential for
soluble salt accumulation and nutrient imbalances.
Applying excess and leaching was easier in general than
testing the media to see if nutrients were present. It is
interesting that the rates of leaching that were
recommended, 10 to 20%, have had little effect on
preventing soluble salt accumulation in our researeh. As
many growers found out it takes 40 to 60% leaching with
constant liquid fertilization of 200 ppm or more to keep
fertilizer levels from increasing. (See Figure) In some
cases 300 ppm or more were being recommended so even
greater leaching was needed. Recommendations for
leaching were not refined to account for differences in
water quality. Everyone leached to avoid problems.
The imgation and fertilization practices and the root
media that evolved over the last 25 years have helped many
greenhouse operators be successful. They have also
created a potential problem of water and fertilizer runoff
and percolation from greenhouses. The key point is that
RodMediawpsI(ey
The key to the success of timed irrigations was that
the root media had to be well drained so it could not be
over watered. Well drained root media made it easy for
even untrained growers to grow crops as long as large
amounts of water were applied regularly. The well
drained root media also benefitted greenhouse operations
still using hose watering because it was harder to over
water. Pots that did not dry uniformly could all be
watered and brought to a uniform moisture level.
The porous root media made use of components like
peat, vermiculite, perlite and sand. Perlite and sand which
were often added to increase drainage had little or no
nutrient holding capacity. Root media components like
peat and vermiculite appeared to have a high cation
exchange capacity (CEC) but not in comparison to the field
soil being replaced.
19
If you can’t buy a system to control irrigation, or you
don’t think you are ready for sophisticated technology,
there is an easier way. The most common way of
determining when to water is to lift a few pots and check
the weight. However, when a pot should be watered is
strongly influenced by individual opinion and the general
rule of thumb is often when in doubt, water.
The inexpensive solution is to buy a portable scale. No
matter how little experience they have, our starting
students have been able to learn how to tell when to water
by simply weighing a few plants. All they have to do is
learn how to let plants dry out to the target weight. The
target weight is determined by weighing several plants that
are at the point of requiring watering. This point can be
moist or dry depending on the grower’s preference, but
now it can be reproduced regularly. The drier the plant,
the fewer the number of irrigations over time. Another
method of setting a target weight is to let some established
plants dry out to very near the wilting point and check the
weight. The difference in weight between a watered plant
at container capacity and the weight of a plant near wilting
is an estimate of the available water in the pot. If the goal
is to minimize irrigation frequency, most plants should be
watered when 60 to 70% of the available water is used.
The target weight may have to be increased as the crop
grows, but not much. A simple scale can make irrigations
more predictable the same way a ruler works for taking
the guesswork out of height control.
Controlling the duration of application to limit
leaching can be accomplished in every greenhouse with
minimal investment. The key is to realize that seconds of
irrigation time, not minutes, are important when it comes
to limiting water use. Use some method to measure the
length of time the plants are watered.
w 200 ppm sub
H 200 ppm
0%
w 200 ppm 10-15%
H 200 ppm 20-30%
bd 200 ppm 40-60%
0
2
4
6
8
10
12
14
Volume 40, Number 1
16
WEEKS FROM PLANTING
The effect of 200 mg/liter N & K applied to 6 inch
poinsettias at various leaching fractions on root
media EC.
watering, media and fertilization are obviously related to
each other. Only through understanding the relationships
between irrigation, fertilization and root media can we
work to solve the runoff problem in a timely and
economical fashion. The goal of every greenhouse operator
should be to develop economical irrigation and fertilization
methods that optimize the root zone
are
environmentally sound.
Root Media Selection
Root media can be selected for higher water holding
There are many different methods to manage water,
fertilizer and media. Some of the methods are very simple
and low cost while others require significant investments.
Subirrigation can eliminate the runoff problem, but many
greenhouse operations are not ready for subirrigation. The
first step in water management for these operations is to
limit or eliminate the waste or runoff so there is little or
nothing to collect and recycle.
capacity. For example, rockwool adds water holding
capacity when blended with peat.
Growers must
remember however that higher water holding capacity
means the frequency of watering must be reduced. The
media should be allowed to dry out or we will be back
where we were 30 years ago.
Leaching must also be minimized if there is to be any
advantage. One media may hold up to twice the available
water of a second media. This could cut the number of
irrigations needed in half. However, the amount of runoff
will be the same if the leaching fraction is kept at 30 or
40%. Leaching must be minimized.
In some cases, just filling the pot more or filling them
thoroughly and uniformly will increase water holding
capacity and decrease irrigation frequency. Careful
watering to reduce media shrinkage will also help. Hose
watering goes faster with higher flow rates, but more water
and media end up in the pot with slow flow rates. The
person on the end of the hose becomes even more
important. Remember that sometimes high flow rates are
Irrigation Scheduling
Scheduling irrigation frequency
based on
environmental conditions and careful control of the
irrigation duration will control water and fertilizer runoff.
Most greenhouse operations do not currently have the
ability to automatically control irrigation based on
environmental conditions.
However, a variety of
computers and irrigation schedulers with this capability are
available and easy to use. Cost seems to be the mqjor
constraint. Labor savings should be considered as well as
the limited availability of qualified labor when considering
investments in irrigation systems.
20
-
January, 1991
Volume 40, Number 1
fertilizer. As long as some nutrient charge is present in the
root media (60-100 ppm N, 5-10 ppm P, 100 to 150 ppm
K, 50-100 ppm Ca, 30-50 ppm Mg by saturated media
extract), watering in with fertilizer concentrations of more
than 100 ppm is a waste of fertilizer. Watering with little
or no leaching and clear water the first week has given us
excellent results. Levels above 200 ppm nitrogen should
rarely be needed during production if applied regularly.
Our poinsettias for classes will be fertilized primarily with
1/4 pound potassium nitrate and 1/4 pound ammonium
nitrate (calcium nitrate and phosphoric acid later) per 100
gallons started one week after planting. (We have high
alkalinity water with 80 ppm Ca++.) The poinsettia can
require large amounts of water under some conditions and
the leaching that occurs can make it seem like more
fertilizer is needed.
used to get a fertilizer injector to work properly. Make
sure the injector works properly at lower flow rates. In
some cases a mixing tank may be need.
There is not very good information about cation
exchange capacity of soilless potting media and how much
effect it can have on fertilization requirements and runoff.
This is an area that needs work. Higher nutrient holding
capacity may not be needed if fertilizer is applied regularly
at low levels and with reduced leaching, or if resin coated
fertilizers are used.
FertilkWhenNeeded
Why should growers leach? Many times applying
clear water with no leaching can allow time for the
fertilizer in the media to be used by the plant rather than
washed away. In many cases in the United States, water
quality is good enough that leaching should almost never
occur. If salt levels are high due to fertilization, stop
fertilizing. Recognize that there are greenhouse operations
that would be out of business if they stopped leaching
because of poor water quality. How do you know what to
do? Water and media analysis.
Many growers do not know the level of nutrients
available in the root media. It has become easier to leach
heavily with a known concentration then to test the media
and find out what is needed. The lack of media analysis in
the greenhouse is possibly a result of too little time and
labor to do the job or a lack of expertise in how to do it.
Educating growers about media analysis methods should be
one of our highest priorities for the coming year.
To use the example of our beginning students again,
they could not be a very effective grower without a soluble
salt meter. Weekly media analysis for pH and EC is one
of the first things they learn. It is a tool they can use to
know how much fertilizer is present and whether more is
needed. Fertilizing only when needed based on root media
analysis and graphical tracking of EC can greatly reduce
the amount of fertilizer applied, and make better crops.
Our research indicates in many cases too much
fertilizer is applied. We have worked mainly with bedding'
plants and poinsettias, but have data on Easter lily also.
These crops require relatively little fertilizer as long as
nutrient levels are maintained in the media at the proper
level. The key is regular application, controlled leaching,
and weekly analysis of media EC. Weekly checking pH
and EC will prevent most nutritional problems growers
experience.
One of the other problems we face, however, is that
current recommended root media analysis levels may be
too high. Some growers are working very hard to reach
levels recommended on a soil test. Not only are the high
levels recommended not needed, but with heavy leaching
they may never be attained. Not even with 400 ppm
nitrogen applied constantly.
Poinsettias are often referred to as "heavy feeders".
We have completed seven experiments over three years and
in each case poinsettia production required very little
ReducingExcess leaching can be avoided with a variety of
techniques. Irrigation systems need to be designed to
provide uniform pressure and water flow at all locations.
With uniform water application, pulsed application of
water, for example 2 applications of 1 minute instead of 1
application of 3 minutes, will use less water and reduce or
stop leaching. Low volume drip applicators will help if
water quality is acceptable and the drippers do not plug.
Use of wetting agents to assure rapid wetting of dry root
media and to reduce channeling of water down the sides of
pots can also reduce leaching and the volume of water
applied.
Fertilizer concentrations can also be reduced so less
leaching is needed. Another way of looking at this is that
if the leaching is reduced, the amount of fertilizer will have
to be reduced. The root media availability of nutrients and
soluble salts is a function of both the concentration and the
volume leached. In one experiment, we applied 200 ppm
N with 12%leaching (ex: 16 fluid ounces applied and 2
ounces leached) or 400 ppm N with 50% leaching (ex: 40
fluid ounces applied and 20 ounces leached) to six inch
poinsettias. The difference was 5 times as much fertilizer
applied. Both strategies resulted in a similar EC level in
the root media (see Figure) and still provide more than
what was needed to grow a good 6 inch poinsettia. Only
100 ppm with 12%leaching was needed.
If water quality is poor or saline, EC > 1.25 mS,
instead of or in addition to leaching, try to lower irrigation
water EC by changing water sources, using rain water,
blending water sources, or water treatment like reverse
osmosis. More growers need to consider collecting and
using rain water, particularly when alkalinity is a problem.
Water collection trays can be used with overhead
irrigation systems or hand watering. These trays provide
+I type of subirrigation and greatly increase the efficiency
of overhead irrigation. This is a low investment approach
which can have a major impact on water and fertilizer use.
Remember that leaching is reduced and so should fertilizer
concentrations.
21
-
similar to a manure holding tank. Above ground water
silos are available but would require pumping and lifting
the water.
Only a limited number of greenhouse
operations are currently collecting runoff in an open
system. Occasional testing of the water may be needed.
Based on the limited information available to me, there
has not been the problem of rampant disease spread that
is often expected with open collection of runoff water.
Where the water goes and how it is collected will determine
the potential for pathogen problems. The temperature and
aeration level during storage also is probably important.
Some form of water treatment may be desired when
the water is recirculated. At least two very large
horticultural operations have chosen to treat the
recirculated water with chlorine. The other alternative
that is available and used by some greenhouses is the
bromine biocide, Agribrom. Agribrom has been shown to
be safe to plants and when used properly will kill algae and
other organisms in recirculated water. There are some
growers in Michigan treating fresh, nonrecirculated
irrigation water with Agribrom. Heat treatment of water
is another alternative that is being tried in Europe.
Q-O
POOppm 12% LEACHING
w 400ppm SOX LEACHING
5
v,
E
- 4
0
W
5
D
3
W
I:
c 2
0
1
0
0
2
4
6
8
10
12
14
Volume 40, Number 1
16
WEEKS FROM PLANTING
Low Cost of Water and Fertilizer
Since water and fertilizer costs make up only a small
percentage of total costs, conservation has not been
considered economically important. The actual cost of
fertilizer is less than 1to 2% of total production cost per
pot in most cases. Small savings in water and fertilizer
cost can mean significant increases in profit per unit
however. A savings of 1cent per pot is a 10% increase in
profit if you only make 10 cents per pot.
The
environmental and regulatory costs of excess water and
fertilizer use must also be considered.
Not all greenhouses have problems with fertilizer
runoff. My observation is that for smaller greenhouse
operations, the cost of a bag of fertilizer i s a significant
cost. Fertilizer is used sparingly, when it is needed, based
on the appearance of the plants. Larger greenhouse
operations that buy fertilizer by the pallet or truck load
tend to use fertilizer more liberally. Fertilizer cost is not
that important to them. These operations usually fertilizer
regularly based on recommended rates.
Subirrigation
Rather than using open systems that allow for
contamination of the water, the use of subirrigation with
recirculated solutions provides the most efficient and
thorough method of controlling water and fertilizer runoff.
Several methods are available, the main ones being flood
benches, flood floors, and flowing water in troughs. There
is no doubt that they work, but cost can be a real barrier.
We have done experiments with subimgation of
poinsettias, Easter lilies, chrysanthemum, geranium, and
bedding plants. Despite the many advantages, investment
in these systems should only be made with careful planning
to cover the cost. Flood floors may be the affordable
answer for many growers.
SIlmmarY
The bad news is that many of the new ideas being
suggested are contrary to what has been recommended for
the past 20 years. Implementing these ideas will require
training growers and greenhouse workers. The good news
is that there are several areas for improvement with our
current approaches to fertilization and irrigation.
CoUeding and Recycling Runoff
Most of the suggestions so far have been directed at
limiting runoff or the need to collect excess water. For
most greenhouse operations it will be more economical to
limit runoff then to collect it and reuse it. Runoff can be
collected when possible and the water reused. The type of
watering system and greenhouse floor will determine how
excess water is collected.
With very porous soils that allow water to percolate
quickly, cement floors would probably be required.
Cement floors are not economically feasible for many
greenhouse operations. If floors are going to be poured,
they should be floors suitable for subirrigation and runoff
will no longer be a problem. With heavy, clay subsoils,
field drains can be used to collect runoff into a central
location. The water holding area can be an earthen pond,
a vinyl lined pond, or an in ground cement reservoir
John Biernbaum is an Associate Professor in the Department of
Horticulture at Michigan State University. The information in this
handout is not to be reproduced or published without the consent of Dr.
John A. Biernbaum, Department of Horticulture, Michigan State
University, East Lansing, MI 48824. This research has primarily been
funded by the Michigan AgricultureExperiment Station and the American
Floral Endowment. Additional support has been provided by The
Bedding Plant Foundation, The Glowkner Foundation, The Western
Michigan Bedding Plant Association, Greenhouse operatorssupportiveof
MSU research, and manufacturers and suppliers of greenhouseproducts.
The research reported is largely the work of Renee George, Mark
Yelanich, and Bill Argo, graduate research assistants.
22
-
January, 1991
Volume 40, Number 1
Soil Test Interpretation
and Recommendations
The information within this article was developed to serve as a quick reference for
interpretation of floriculture soil tests by the University of Minnesota. In addition to supplying
the recommended ranges for the various factors quantified in the soil test, some
recommendations for common problems are also supplied. Specific recommendations for your
situation can be obtained by calling me, John Erwin, at /612)-624-9703 . Making sure you
have both a recent water test as well as the soil test are recommended. It is very possible that
you may receive the 'voice mail' system when you call. This means that either I am out of my
office or am on another line. Alwavs leave a r n e s s a I will return your call as soon as
possible.
Test Parameter
o r Nutrient
PH
Recommended
Acceptable
6.2-6.8
5.8-7.2
Soluble Salts ( S S )
80- 140
50- 150
Nitrates (NO31
150-250
100-350
Ammonium (NH4)
0-10
0-15
Phophorus ( P I
10-15
5-20
Potassium ( K )
50- 100
30- 120
Calcium (Ca)
50-200
25-300
Magnesium ( M g )
30-50
20-60
Sodium (Na)
10-40
5-60
I r o n (Fe)
0.20-0.50
0.10-0.70
Manganese ( M n )
0.50- 1.50
0.30- 1.75
Zinc (Zn)
0.10-0.50
0.05-0.75
Boron ( B )
0.05-0.25
0.02-0.50
23
Typical
Volume 40, Number 1
Pro dems
High pH - High pH is by far the most common problem in greenhouse media in the upper
midwest. The best solution is to amend the water and/or fertilizer solution before it is applied
to the pot1 If pH is high, a one time quick method to drop the pH is recommended. The easiest
way to do this is by adding acid to your water and drenching the media. The exact amount of acid
which is needed to drop your media pH is difficult to determine; it varies with water source,
and media and fertilizer composition. However, a 'rule of thumb which has worked is to add 2.03.5 ounces of 75-85% phosphoric acid to 100 gallons of water (final solution) as a 1 time
drench. In general, this will drop the media pH 0.5-1.0. Do not add more than this! Test media
before attempting to adjust further.
High Soluble Salts - The easiest way to solve a high soluble salts problem is to 'leach' the
media. Leaching is simply watering with clear water for an extended period of time. Remember
that your pH will probably increase since water pH in the upper midwest is generally high.
High Ammonium - High ammonium levels can result in ammonium toxicity. High ammonium
often results from using fertilizer which contains ammonium during a period of the year when
both light levels and temperatures are generally lower. Ammonium toxicity is prevalent from
October 15 to March 15. Ammonium tends to build up more easily in media which contain soils.
Ammonium toxicity is aggravated by high pH, low potassium, and cool temperatures. If
ammonium levels are high 1) stop using fertilizers which contain ammonium, 2) leach the
media, 3) lower pH, and 4) increase the potassiuh content of the media.
Low phosphorus - Phosphorus levels can be increased rapidly by applying a 'starter'
fertilizer high in phosphorus as a 1 time application. Generally if phosphoric acid is being
injected into the water to modify pH, the phosphorus requirements for plant growth are met.
Low Potassium - Potassium deficiency is characterized by a yellow 'speckling' on the leaves.
Increase the amount of potassium nitrate which is in your fertilizer mix. A potassium
deficiency is aggravated by nitrate levels more than 3 x's that of the potassium level. Always
try to maintain a potassium level 1/3 of that of the nitrate level.
High Calcium - High calcium usually suggests high water alkalinity. High calcium is usually
not detrimental, however, it can aggravate a magnesium deficiency. Therefore, make sure that
magnesium levels are as close to 1/3 that of the total calcium levels in a crop.
Low Magnesium - Magnesium leaches readily from a medium. Therefore, it is often necessary
to add magnesium through continuous feeding or with regular single drenches. Drench a
minimum of 1 time each month with magnesium sulfate (Epsom salts, MgSo4) at a rate of 8
ounces/l 00 gallons. Alternatively, apply 2 ounces MgS04,lOO gallons water in a continuous
liquid feed program. Do not mix magnesium sulfate and calcium nitrate together; they will
react in the stock tank.
Low Iron, Manganese, and Zinc - Add a micronutrient source to your regular feed program or
drench with a micronutrient source. A good time to do this is in combination with the monthly
magnesium sulfate drench.
High Boron - High boron often results from a high boron content in your water source. Have
the water source tested. It may be necessary to eliminate any micronutrient applications
and/or use reverse osmosis to 'clean' your water. Leach with water.
24
-
January, 1991
Volume 40, Number 1
How To Calculate The Amount Of
Phosphoric Acid
Needed To Neutralize Water Of A Known Alkalinity
Bob Munter and John Erwin
A very common problem in the upper midwest is pH management. Often crops are grown in
what would be considered alkaline media. As a result, crop growth is often depressed due to,
among other things,nutrient deficiencies.
One way to manage pH is to simply neutralize you water prior to watering a crop. High pH
water is neutralized by adding an acid to the water. To determine the amount of acid which must
be added to neutralize water a water sample must be taken prior to adding fertilizer and sent to
the soil testing lab to determine the 'alkalinity' of your water. Once the alkalinity of your water
has been determined, the following computations can be done to determine the amount of acid you
must add per gallon of water to result in a pH of 7.0. The most common acid used to neutralize
water is phosphoric acid.
1.
Basic Information:
Strength of phosphoric acid: Stock solution is 44.4 normal.
75% solution is 33.3 normal
Alkalinity is reported as milligrams of calcium carbonate (CaC03) per liter of water
Molecular weight of CaC03 is 100
Equivalent weight of CaC03 is 50
General formulas for equivalents, volumes, and normalities:
milliliters (ml) x normality (N) = ml x N
since ml x N = milliequivalents
rnl x N = millieqivalents
mghquivalent weight
=
milliequivalents
II. Example problem:
Given, 1 liter of water that has an alkalinity of 270 mg CaCO3/liter
What volume of a 75% phosphoric acid solution (33.3 N) is required to neutralize the
270 mg CaC03 in 1 liter of water?
25
111.
-
January, 1991
Volume 40, Number 1
Solution:
270 mg CaC03 (alkalinity) / 50 (equivalent weight) = 5.4 milliequivalents CaC03/
liter.
ml x
33.3 (normality) = 5.4 (milliequivalents CaCO3/liter)
ml = 5.4 (milliequivalents CaCOa/liter) /
phosphoric acid (H3P04).
33.3 (normality)
=
0.1622 ml
Therefore, 0.1622 ml of 75% phosphoric acid is needed to neutralize 1 liter of water with an
alkalinity of 270 mg CaC03Aiter. To determine the amount of acid required per gallon,
multiply the amount of acid required per liter by 3.785. In our example, 0.61 ml of
phosphoric acid would be required per gallon of water.
/
J
Z
Remember!
1) Understanding the effects of temperature on Easter lily growth is very important to
successfully force an Easter lily crop. The rate of leaf unfolding on an Easter lily is dependent
on the averaae dailv. ternperature which plants are grown under. In contrast, the morphology,
or appearance, of the Easter lily is dependent on the relationship between the day and night
temperature, or DIF. Easter is early this year. With an early Easter plants will probably need
to be grown somewhat warm (>68oF) to insure flowering on time. To have 50% of your crop in
flower 3 days before Palm Sunday you will need to be at visible bud around the 17th of
Februarv this v e gr. Leaf count! Exact information on how temperature affects Easter lily
growth can be found in the October issue of the M.F.G.A. bulletin.
2) Apply fungicides to your lily crop regularly, i.e. monthly. Do not wait for root rot to occur;
it always does!
3) Try to minimize A-Rest use. A-Rest tends to encourage lower leaf drop late in the season.
4) Give your lilies adequate space. This is especially important late in the season, i.e. after
visible bud. Crowding lilies late in the season will result in lower leaf drop.
5) Take the time to have full soil tests done on your bedding plant media. Initiate a preventative
fungicide for your bedding plant crop. Do not wait for a problem to occur.
6) Crowding plants reduces branching. Do not crowd geraniums early in development.
7) Hydrangea flower color is dependent on a number of factors. Usually dormant plants are
shipped to us 'pretreated' for a specific flower color. However, the way we treat plants once
they have arrived can greatly affect whether plants actually are blue or pink at flower. A
summary of what factors affect hydrangea flower color is shown below.
26
-
January, 1991
Volume 40, Number 1
8) Watch ammonium levels on zonal and ivy geraniums. This is the time of year we tend to have
ammonium problems on each of these crops (especially on stock plants).
9) Graphically track lily and chrysanthemum crops this spring. Do not let stem elongation get
away from you1
Editor's Notes
Easter Lilies seem late! - Most Easter lily crops in the Twin Cities are somewhat late.
Emergence has been slow, and non uniform. Leaf count! Early counts suggest around 80-85
leaves per plant. You will probably have to grow your crop warm. Also, because of the
variability, sorting will be necessary into different environments to even up the crop.
Control Thrips - Control thrips now before tomato spotted wilt virus is evident! Isolate new
shipments of plants to insure they do not have thrips or tomato spotted wilt virus. If plants are
suspected of having TSWV, have them tested. Last year TSWV was found on tomatoes, new guinea
impatiens, gloxinia, and cineraria.
27
-
January, 1991
Volume 40, Number 1
Future Meetings
1.
Minnesota Flower Growers Meeting
Tuesday, February 12
Greenhouse Tours - Gerten's Greenhouse and Walter's Greenhouses
Speaker: Mike Heger - Production of new and exciting perennials
I I. Minnesota
welcomes t h e
Association.
Commercial
Flower
G r o w e r s Association
Puget Sound Commercial Flower Growers
Thursday, March 14
Puget Sound Commercial Flower Growers arrive and check into the
Bloomington Marriott Hotel (Marriott provides airport shuttle bus
service)
2:30 p.m. - Bus leaves Mariott hotel to tour Malmborg's and Len Busch Roses
6:OO p.m. - Regular M. F. G. A. meeting at the Marriott
Speaker: Harry Tayama (The Ohio State University)
Topic: Bedding plant production
Cost: $17.00
Friday, March 15
7:30 a.m. bus departs Bloomington Marriott
Tours of:
National Polymer
Jim Murphy Films
Bachman's growing range
Bailey's Nursery
Hermes
Linder's
University of Minnesota
5:30 p.m. bus returns to Bloomington Marriott
Cost for tours and box lunch: $14.00
Saturday, March 16
9:00 a.m. - bus departs Bloomington Marriott
Tours of:
Rosacker's
J.R. Johnson's
Wagner's
Bachman's (Lyndale)
4:OO p.m. - bus returns to Bloomington Marriott
Cost for tours: $16.00
6:OO p.m. - North Central Florist's Association President's Ball
(Minnesota and Puget Sound Flower Growers are invited)
cocktails, dinner, Celtic concert, and dancing
Cost: Individual $50.00, Couple $90.00
28
-
January, 1991
Volume 40, Number 1
Sunday, March 17
Symposium sponsored by North Central Florist's Association
9:00 a.m. - 4:OO pm.: "Moments of Truth", Managing Customer Service
Speaker: Frank Quisenberry
Cost: $25.00/$28.50 (lunch included)
9:00 a.m. - 4:OO p.m. - Design Symposium
Cost: $25.00/$28.50 (lunch included)
I I I.
Minnesota Flower Growers Association Meeting
Tuesday, April 9
Greenhouse Tours: To be announced
Speaker: To be announced
Topic: How the 'Minnesota Grown' program can benefit your business
This bulletin was composed and edited by Dr. John Erwin, Assistant Professor and Floriculture
Specialist, Department of Horticultural Science, University of Minnesota, 1970 Folwell Ave.,
St. Paul, Minnesota, 55108. Phone:(612)-624-9703, FAX:(612)-624 4941. Opinions and
opposing comments regarding the content of this bulletin are welcome and encouraged. This
bulletin is published in cooperation with the Minnesota Commercial Flower Growers Association
and the University of Minnesota Extension Service. The bulletin is distributed to members of
the Minnesota Commercial Flower Growers Association. Questions regarding membership in
this organization should be directed to Mark Whitman, Len Busch Roses Inc., 4045 Highway
101, Plymouth, Minnesota 55446. Phone: (612)-478-6077.
29
-
January, 1991
Volume 40, Number 1
Table Of Contents
Caladium Production .
Producing Cut Flowers - Florist Statice
.
.
Greenhouse Nutrition - Nitrogen
Research Update
Water Management .
Soil Test Interpretation and Recommendations
How To Calculate The Amount Of Phosphoric Acid Needed To Neutralize Water Of
A Known Alkalinity .
Remember! .
Editor's Notes .
Future Meetings
1
7
11
14
19
23
25
26
27
28
Issued in furtherance of cooperative extension work in agriculture and home economics, acts of May 8 and June 30, 1914, in cooperation with the US.
Department of Agriculture. Patrick J. Borich, Dean and Director of Minnesota Extension Service, University of Minnesota, St. Paul, Minnesota 55108. The
Universityof Minnesota, including the Minnesota Extension Service, is committed to the policy that all persons shall have equal access to its programs,
facilities, and employment without regard to race, religion, color, sex, nationalorigin, handicap, age, veteran status, or sexual orientation.
MINN. COMMERCIAL FLOWER GROWERS ASSN.
MINNEAPOLIS, MN. 55404
BULK MAIL
U. S. POSTAGE
PAID
ST. PAUL, MN
PERMIT NO. 4170

The Minnesota Flower Growers Bulletin

Transcription

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