MACHINERY SYSTEMS IN TROPICAL AGRI

MACHINERY SYSTEMS IN TROPICAL
AGRI-FOOD CHAINS
Francesco Garbati Pegna
Lesson 3a
Power (muscles)
Human power
As a source of power, the human being operates essentially like a
heat engine, with built-in overload controls or regulators.
Chemical energy input in the form of food is converted into
energy output, some of which is useful for doing work.
On the average, a healthy person in temperate climates
consumes energy at a sustainable rate of only about 300 W, while
in tropical climates, as a result of heat stress the rate is reduced
to only about 250 W.
Many tasks for agricultural production can be performed only at
higher rates of energy consumption.
CIGR Handbook Vol 3
Only about 25 % of the energy consumed when handling relatively
easy tasks such as pedaling, pushing or pulling is converted to
actual human work output. Under more difficult work conditions,
the efficiency of converting consumed energy to physical work
may be as low as 5 % or less. This means that, at the maximum
continuous energy consumption rate of 0.30 kW and conversion
efficiency of 25 percent, the physical power output is
approximately 0.075 kW sustained for an 8–10 h work day.
Naturally, higher rates can be maintained for shorter periods only.
The farmer should employ the preferred modes of human power
application such as pedaling or simulated walking.
Human Power Consumption for
Various Farming Activities
Some Field Operation Rates by Farmers
Using Hand-Tools
The fact that many primary agricultural production operations
demand higher rates of energy than the maximum sustainable rate
of energy consumption by humans necessitates rest periods in
manual work. The rest period required can be estimated using the
formula:
Tr = 60·(1 – 250 /P)
where,
Tr = required rest period in min/h of work,
P = actual rate of energy consumption in watts.
It must be noted also that an appropriate rest period, as estimated
using the above formula, is a physiological necessity inherent in
manual work.
Power is the major limitation to increasing the area cultivated
by the hand-tool farmer.
The problem is not necessarily with the tools used, especially
for primary production operations, since efforts made to
redesign them have yielded no significant improvements .
The toil, drudgery, and severe power constraint on timely field
operations, which limit production and earning capacity, are the
inherent characteristics of peasant farmers using hand-tool
technology:
changing the technology means changing the farmer’s status.
CIGR Handbook Vol 3
A machine is a device or mechanical contrivance consisting of
two or more relatively constrained components which is energized
by a power source to transmit and/or modify force and motion to
accomplish some desired kind of work.
A tool is a human powered instrument or implement usually
without parts that move relative to one another, like a hoe, a
dibber, or the like, used to facilitate mechanical manual operations.
CIGR Handbook Vol 3
Hand tool technology is the simplest and most basic level
of agricultural mechanization: it consists in the use of
tools and simple implements using human muscle as the
main power source
Field operations are tasks performed in the field at different
phases of crop production.
The major operations include:
- land preparation,
- planting,
- weeding,
- harvesting.
Based on these operations, the tools/machines used are classified
into: land preparation tools/machines; planting tools/machines;
weeding/cultivation tools/machines; and harvesting
tools/machines.
CIGR Handbook Vol 3
Hoe: used for land preparation, planting, weeding,
harvesting
Machete/Cuttlass: used for: land preparation,
weeding and harvesting
Spade: used for land preparation and harvesting
Dibber, Planter: used for sowing and planting
Sickle, Scythe: used for harvesting
Diggers, lifters: used for harvesting
Axe, Fork, Rake, Shovel and Wheelbarrow: for
handling and moving
Hand-operated machines: for planting and sowing
Post-harvest operations are those activities undertaken to
transport, process, transform, preserve or store harvested
agricultural products in order to enhance their economic
value by increasing their nutritional value and availability over
time and space and therefore, their price or market value.
CIGR Handbook Vol 3
The major post-harvest activities include:
- threshing,
- cleaning,
- sizing,
- shelling,
- peeling,
- grating,
- cutting, slicing, chipping,
- grinding, milling, cooking,
- drying,
-pasteurizing,
- fermentating,
- handling and transporting.
Manual Work
Gender specificity in manual work
Some facts on rural women
- Presently, around 842 million people are suffering from hunger world-wide,
especially in Asia and sub-Saharan Africa. Sixty per cent of them are women
and girls.
- Women make a significant contribution to family farming.
- Women account for an average 40 per cent of the agricultural labour force.
The share reaches from 20 per cent in Latin America to 50 per cent in East
Asia and sub-Saharan Africa, and in some West African countries, it is up to
80 per cent.
- Only around five per cent of all agricultural extension services reach and
benefit women farmers. Topics of special concern to women are frequently
only insufficiently addressed by male advisors, while just a few advisors are
women.
- Women benefit from a mere 10 per cent of financial support for agriculture
and forestry or fisheries.
Rural 21 Vol. 48 Nr. 2/2014: Family Farming
Gender specificity of agricultural work
In Vietnam, 53% of the farming population
is female and 73% of these women are
employed in the agricultural sector. In
addition, women are involved in trading
the agricultural produce in local markets
and marketing cooperatives.
Traditionally, the first stages of rice
cultivation are male designated and the
latter stages female designated. However,
the traditional task division has changed
due to lack of male labour.
Women are thus increasingly involved in all
stages of rice production.
Gender division of labour in rice farming
Tasks
Male Female Both
Clearing field
x
x*
Ploughing
x
x*
Making bunds
x
x*
Preparation seedbed
x
x*
Sowing seedbeds
x
Transplanting
x
Irrigating
x
x*
x
Fertilizing
x
x*
x
Pest control
x
Weeding
x
Harvesting
x
Processing
x
Marketing
x
* in absence of male labour
Source: UNIFEM, 1988
Does mechanization influence gender specificity
in agriculture ?
…... in some cases it was only the work undertaken by men that
was mechanized. The tasks traditionally performed by women
remained unchanged although the work demanded of them
increased as the area planted and the yields increased…..
Add other ……..
Manual Tools
Characteristics of hand tools
Manual tools can be quite different depending on the area in
which they are used. In some countries the shape and size of
hand tools can vary within the same region, at a distance of few
kilometers.
These differences are due to different working conditions (i.e.
altitude, slope, soil, crop, climate, physical characteristics of
workers, availability of materials etc.)
Nowadays globalization has erased major cultural differences
and traditions but still most tools are available in different
choices depending on the function they have to be used for.
These different characteristics must be known in order to make
the best choice and provide for optimal working conditions.
Tools by Angelo B
-Cav. Mario Valsecchi & Figli srl-
Angelo B is an Italian brand
with a complete offer of hand
tools for agriculture
http://www.angelo-b.com
Different sickles for harvesting E. Guineensis fruits
Different shapes and sizes for simple hand sickles
and hay hand sickles
Ralph Martindale
Machete (cutlass) types for Africa
Ralph Martindale
Machete (cutlass) types for Latin America
Characteristics
As other hand tools shovels can be available in many different
shapes and sizes of the shovel and of the shaft
Fiberglass
Shovels
Angelo B
Hoes
Angelo B
da: Tools for Agriculture
I.T.-GTZ/GATE, 1985
da: Tools for Agriculture
I.T.-GTZ/GATE, 1985
The low-technology characteristic is important because it implies
that these implements can be, and generally, are fabricated by the
farmers themselves, as well as by local artisans and blacksmiths,
so that their supply is largely in response to their demand.
Although local manufacture in itself is a good thing and should be
encouraged for various economic reasons, it must be noted that,
given the intrinsically low-volume, the lack of formal scientific
basis, and the absence of quality control in the production
process, the products generally are of low quality.
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There are many factors that combine with capital cost
considerations to make the economics of hand-tool technology in
developing countries quite intriguing.
With small and usually irregularly shaped plots planted with a
mixture of crops, a cropping system based on the use only of
primitive hand-tools that may be old and worn out, leads to
poorly cleared land, poorly tilled soils and poor planting in
irregularly formed rows: the outcome is inevitably a poor harvest.
Under these circumstances, with low cost advantage and low
productivity, the economics of peasant agriculture using HTT,
exhibits the vicious cycle of poverty-begetting-poverty.
CIGR Handbook Vol 3
Animal Traction
Draught animal technology
Refers to implements and machines utilizing animal
muscle as the main power source.
Animal Traction
Animal traction constitutes a possibility for enhancing
the energy level of the agricultural system
Cattle, buffaloes, horses, donkeys and mules are the main draft
animals. Camels, elephants, llamas and yaks also may be used.
The factor limiting the use of animals for work is their reduced
energy potential, which is determined by characteristics and
working ability of the species.
Energy is provided to animals from feeds previously
metabolized into fats and carbohydrates, and then assimilated
in muscles. The energy output required for such processing is
not well known.
A draft animal power (DAP) unit (i.e., animal plus equipment),
which exerts a tractive force, can be compared with a system
consisting of a resistant part (equipment) and a power unit
(animals). The energy accumulated by animals is partially released
in a mechanical form when pulling equipment or carrying a load.
CIGR Handbook Vol 3
Animal traction has been used in Asia for thousands of years. Today, it remains a
vital component of a farmer’s life. Draft animals, usually an animal team controlled
by one person, are conveniently maintained and trained. Female working animals
are common. Water buffaloes and cattle are worked mainly in pairs for tilling paddy
fields, rice threshing and transport. Elephant numbers are decreasing. They mainly
assist with logging. In India, donkeys, horses, mules, camels and yaks are used for
pack transport, but rarely for farm cultivation.
Animal traction was introduced into Latin America several centuries ago by
colonists. In the tropical zone, cattle are worked in pairs, usually controlled by one
person, for plowing and transportation. In the highland and plateau areas of certain
countries (e.g., Mexico, Chile, Argentina, Brazil), horses, donkeys and mules are
preferred to oxen because they walk faster and prove better suited to pack and cart
transport
In North Africa, cattle, donkeys, horses and camels are still used widely for water
raising, pack transport and carting. As power mechanization has developed, animal
traction for farming and transport has strongly decreased in plain areas, but not to
the same extent in highland areas.
Animal traction in sub-Saharan Africa, excluding Ethiopia, was introduced for
farming at the end of the past century. The number of work animals is low
compared with the size of the continent. They are widely used in semiarid and
subhumid areas. In cotton and groundnut zones of western Africa and some
southern African countries. This technology also can be found in some humid
areas, but is almost nonexistent in vast countries such as the Democratic Republic
of Congo. In most cases, two or three persons are required to work with a team,
which shows the low training level of animals. These are often excessively weak
because they are underfed. Donkeys and horses, lower in number than cattle, are
used in semiarid areas for light work (i.e., sowing and weeding) and also for cart
and pack transports. Cattle principally are worked in pairs, mainly for plowing and
ridging, and to a lesser extent for sowing, weeding and transport purposes.
In Industrialized Countries Animal Traction is a memory of old times
Which rarely perpetuates nowadays
In Industrialized Countries Motorization has brought to
abandoning of Animal Traction which still exists only in
particular niches
Modern
technology:
disc brake !
Modern Animal Traction
Old style animal traction applied today
(Cuban energy crisis consequent to Soviet Union collapse)
Animal traction in areas where breeding of cows is
a well established tradition
The sustained effort corresponding to a working time of about
2–3 h per day, at a normal speed (0.6–0.8 m/sec), determines
the animal team’s capability.
According to animals and working conditions, the next-tooptimum effort is between 9% and 12% of the live weight for
oxen and buffaloes, between 12% and 16% for donkeys and
camels.
Knocking against obstructions results in a maximum
instantaneous effort: this equals the animal live weight in value
and determines strength constraints for the materials to be
used in farm implements.
DE = energy expenditure at work
Sustainable power of individual animals in good condition
Animal
Typical
weight kN
(kgf)
Pullweight
ratio
Typical
pull N
(kgf)
Typical
working
speed
m/s
Power
output W
Working
hours per
day
Energy
output
per day
MJ
Ox
4.5 (450)
0.11
500 (50)
0.9
450
6
10
Buffalo
5.5 (50)
0.12
650 (65)
0.8
520
5
9.5
Horse
4.0 (400)
0.13
500 (50)
1.0
500
10
18
Donkey
1.5 (150)
0.13
200 (20)
1.0
200
4
3
Mule
3.0 (300)
0.13
400 (40)
1.0
400
6
8.5
Camel
5.0 (500)
0.13
650 (65)
1.0
650
6
14
Note: For animals of different weight the power output and energy output per day may be adjusted proportionately
Source: Tools for Agriculture, 1992
In-depth knowledge of the factors influencing the work achieved
by animals is required. Some of these can be controlled by
farmers, others cannot
A harnessing system is a set of elements involving a harness, driving
fittings (steering ropes, bridles) and single or multiple hitching
systems (abreast or in tandem). For carting, additional fittings can be
used to assume other functions such as the cart balance (back strap,
belly strap), braking, and reversing (breeching strap).
The harness is the main part of a harnessing system. It makes it
possible to optimize the energy potential provided by an animal to
exert a force for pack transport, pulling a cart or a farm implement,
or driving an animal-powered gear
There are various types of harnesses that can be classified
according to the point where they apply work to the animal:
- just behind the horns on the neck (neck yoke)
- on the withers (withers yoke),
- before the shoulders (collar),
- on the breast (breast band or breast strap)
- ………
Yokes are mainly used with bovines. According to the number of
animals harnessed, yokes can be single with a single animal,
double with a pair of animals, or sometimes triple for training a
young animal between two older ones.
Oxen develop their force mainly at the head/neck level
Padding is required between the yoke and the animal’s neck.
Incorrectly shaped or fitted neck yokes, with excessively loose or
thin securing ropes, provoke injury, horn wearing and sawing. This
results in reduced power from the draft animals harnessed.
Head yokes
Neck yokes are tied just behind the
horns. They were widely used in
Europe before the introduction of
power-driven equipment.
Head yokes
Forehead yokes are tied in front of
the horns, and are rather
uncommon. They were known in
Spain and largely popularized in
Switzerland and
Germany.
Mainly used with humpless cattle (Bos taurus) with strong necks and horns,
their form varies from the simplest uncarved wooden pole to yokes shaped
into more or less pronounced bows.
Wither yokes
Withers yokes apply on the withers,
in front and over the shoulders.
They are naturally suited to hump
cattle (Bos indicus) such as zebus.
They can also be used with taurines
as N’Damas.
Withers yokes are predominant in
Africa.
Whatever the type of yoke, lowering the attachment point also requires
lowering the applying points towards the points of the shoulders. This
reduces the slope of the line of draft (an angle of 15° is suitable).
Collars and breast bands
The collar generally is the most suitable harnessing system. A collar
includes a frame for fitting on the animals, padding for protection and
comfort, and a device for hitching an implement.
There are several points to apply a collar to the animal, which results in
a better distribution of forces. Collars are not as widely used as expected
because they are relatively difficult to make, and therefore expensive.
Breast bands are lighter and simpler harnesses, widely used with horses
and mules because of their simplicity and low cost. They prove well-suited
to the conformation of such animals because of their ample breast.
Horses better tolerate draught efforts at the base of the
neck and at the chest level because of he large muscles and
the absence of clavicles
Horse harnessing can be very complex
For heavy duties more animals are connected together to the implements
Multiple connection however lowers efficiency so the power developed by n
animals is always lower than the power developed by 1 animal multiplied for n.
Pooling two animals or more in a team results in a reduced efficiency at an
individual level. If the available power is 1 with one animal, it is only 1.85 with two
animals, 3.10 with four, and 3.80 with six
Farm Equipment for animal traction
Equipment for Transport
Various means are used: riding, pack and cart transport (2-wheeled carts or
4-wheeled trailers), and sledges.
Riding donkeys without any harnessing system is predominant. Camels and
horses are more prestigious. They are harnessed with specific saddles locally
manufactured.
Carrying loads on the back of animals is very common throughout all the
tropical areas. Loads vary between 80 and 100 kg in weight for donkeys, to
300 kg for dromedaries.
Bulky loads are directly placed over the animal’s back and held in place with
ropes;
rigid materials (stones, firewood, water containers) are transported on pack
saddles with a wooden frame fitting on protective paddings;
In-bulk products are placed in symmetrical pannier baskets over the animal’s
Back.
In the tropics, animal-drawn carts are a widely used equipment for transport. In
rural areas, farmers, artisans and traders employ carts for domestic needs (water
and firewood), agriculture (seeds, fertilizers, manure, harvest), trade and social
purposes
The load capacity of a cart (the load a cart can carry across country without
distortion or breaking) is 500 kg with a donkey and 1,000 kg with a pair of oxen.
The tractive force required to move a cart is the product of the total weight of the
load (load capacity + dead weight), by the rolling coefficient (which varies with the
soil surface state) and the slope:
Tr = P · (K + i)
where:
Tr = tractive force (kg)
P = total weight of the load (kg)
K = rolling coefficient
i = slope coefficient (%)
A braking system is required in hilly areas.
Carts may be fitted with wooden or steel wheels. But wheels with pneumatic tires
similar to those on light power-driven vehicles are becoming increasingly
common.
Animal traction traditionally used for transport
Water lifting
Direct transport
Also camels can be used for traction
Use of modern components
Animal power available for work is seldom used with maximum
efficiency. Possible improvements must take into account the whole
system, including the user, the animal, the harnessing system, the
equipment, and all the other factors that determine animal
performance. Long-term improvements must focus on improved
management (feeding, care, training) of animals by farmers, and on
the selection of animals better suited to work. In the short term,
animal performance can be improved significantly through the
selection of appropriate and diversified equipment and harnessing
systems.
Le tropiculteur
T.E. Simalenga, A.B.D. Joubert, Developing agriculture with animal traction
http://www.nda.agric.za/docs/infopaks/Animaltraction.pdf
http://www.sismar.sn/menu.php?page=semo
Figures from:
References
ATNESA - http://www.atnesa.org/ - http://www.animaltraction.com
Practical Action - http://answers.practicalaction.org/ (select Transport/animal traction)
Keywords:
Animal traction, Culture attelée, Tracción animal
Selected readings
T. Davis The Four Principles of Animal Draught, Practical Action
Exercise:
chose and develop a subject concerning Animal Traction
Il riposo – G. Fattori