School Science Lessons
School food gardens for tropical regions
2012-05-12 SPwp
Please send comments to: J.Elfick@uq.edu.au
Preface
Before teaching this project, discuss the content of the lessons with a field officer of the Ministry of
Agriculture and get advice on planting material, planting distances, site for planting, approved mulch,
composting, and control of pests and diseases. Use only the procedures, agricultural chemicals and
insecticides recommended by the local field officer of the Ministry of Agriculture.
Table of contents
6.9.17.0 Fertilizers
6.9.16.0 Legumes, bean, pea
6.9.18.0 Pesticides
6.9.17.2 Soil acidity
6.9.17.0 Fertilizers
6.9.15.4 Boron deficiency
6.34a Chemical fertilizers (Primary)
9.14.0 Composting
6.9.17.1 Fertilizers, strait and mixed
5.18: Fertilizing the soil
6.33 Fertilizing soil (Primary)
9.9.18 Hydroponics, soil-less culture solutions
6.9.15.3 Liquid manure
4.35 Natural fertilizers (Primary
5.25: Plant nutrients from plant ash
12.14.5: Superphosphate production
6.9.15.5 Tests for adding gypsum to the soil
6.9.18.0 Pesticides
16.13.5 Acaricides
6.9.18.4 Active constituent
6.9.18.1 Caution before using pesticides
16.13.8.5 Chemical Pesticides, Poisons
5.22 Control of pests and diseases
5.21 Diseases of plants
6.9.18.2 Dusts
6.9.18.8 Emulsifying agents
6.9.18.9 Granules
16.13.2.0 Inorganic chemical insecticides
16.13.8 Insect repellents
6.9.18.12 Insecticide types - contact, ingestion, systemic
16.13.8.4 Integrated pest management (IPM)
16.13.3.0 Organochlorine insecticides, organochlorides, chlorinated hydrocarbons
16.13.4.0 Organophosphate and carbamate insecticides
6.9.18.6 Persistence
6.9.18.10 Pesticide safety
6.9.18.11 Pesticide safety, FIRST AID
16.13.1.0 Plant extract insecticides
6.9.18.5 Resistance to pesticides
6.9.19.0 Sprayers and dusters
6.9.18.7 Surface acting agents
6.9.18.3 Withholding period
6.9.16.0 Legumes, bean, pea
6.9.16.0 Legumes, bean, pea
6.9.16.01 Legumes, Different legumes
4.29 Bean flower, (winged bean) (Primary)
4.28 Bean life cycle (Primary)
4.30 Bean seeds and pods, (Primary)
41.0 Classification of the common bean species
4.27 Collect bean plants (Primary)
6.9.16.10 Common bean
6.9.16.9 Cowpea
6.6.17.1 Energy from peanuts
5.27 Germinate bean seeds, (Primary)
6.9.16.5 Growth habit of legumes
6.9.16.3 History of legumes
6.9.16.2 Legume cover crops
9.5.12 Legume pod fertilization
9.72 Legume roots, broad bean, clover
4.26 Legumes (Primary)
6.9.16.4 Legumes in the diet
6.9.16.8 Mung bean
6.9.16.6 Planting legumes
7.8.3.6 Prepare bean curd, (tofu, soya bean)
9.155 Respiration apparatus, tests for respiration of soaked peas with limewater,
6.6.10 Respiratory quotient calculation for mung bean seedlings
9.75 Root hairs of germinating bean plant
6.9.16.7 Root nodules
4.3.13 Root nodules, Isolating micro-organisms from root nodules
4.3.12 Root nodules, Nitrogen-fixing bacteria
6.6.4 Tests for respiration of soaked peas with limewater
4.25 Uses of peas and beans (Primary)
6.9.16.1 Uses of legumes
6.9.16.11 Winged bean
6.9.15.3 Liquid manure
Animal manure can be hoed into the surface of the soil where it will act as a mulch and fertilize the soil.
However, if you mix the manure with lots of dry grass it may take nitrogen plant nutrient out of the soil.
Some animal manure such as chicken manure or fresh pig manure may burn small plants if put directly in
the soil. It is best to put animal manure on the compost heap. You can use animal manure directly on
small plants as liquid manure. Hang a sack inside a drum filled with water and put the fresh manure into
the sack. Nutrients will dissolve into the water in the drum. Use this to water around the young plants.
You may have to dilute 1 part of manure water with 3 parts of pure water. This is a good way of using
new manure, but it is smelly.
6.9.16.0 Legumes
See diagram 9.72: Root nodules | See diagram 9.72.1: Legumes: winged bean, pigeon pea, mung bean
See diagram 9.72.2: Winged bean flower
Plants from the bean family called legumes are very important for school food gardens because you can
use them for protein food, as a green vegetable and for green manure and cover crops.
In this lesson teach students to recognize different plants in the legume family. To prepare for this lesson,
collect 3 examples of legumes: food plants, cover crops or green manure, large trees. Also, collect
examples of plants which are NOT legumes.
In this type of lesson. you do not tell the students the answers. Instead you let them look at the plants and
discover a set which have similar characters. The students should find out for themselves what "legume"
means.
Divide the class into groups of 4 to 5 students. Give each group one of each kind of legume and some
plants which are not legumes. Tell the students to look at all the plants carefully and then make a set of
plants which have similar characters. Let the students talk about this.
Go to each group and help the students make their set but do not tell them the answers.
Let the students walk around from group to group so they can compare the sets.
Stop the students from moving about and show them the correct sets. Ask the students to tell you the
common characters of the set. These are as follows: shape of leaves, shape of flower, the number of
parts in the flower and the nodules on the roots.
The roots have lumps on them called nodules. These nodules contain Rhizobium bacteria called which
can use nitrogen gas from the air. When the plant dies this nitrogen in the plant can then be used as plant
nutrient by other plants.
Now you can tell the students that the set of plants which look the same are all members of the legume or
bean plant family. Ask them if they could find other legumes in the gardens and in the bush. You can give
the students some work for the next lesson tell them that each student must bring to the next class a legume
plant which they did not see in the class today.
Resource material, Legumes
Legumes are plants of the bean family (Fabaceae). Most of the plants have lumps on their roots called
nodules. Rhizobium bacteria can live in these nodules and use nitrogen gas from the air. When the legume
plant dies and rots other plants can use this nitrogen. In this way legumes improve the fertility of the soil.
When you dig a legume crop into the soil it is called a green manure.
Leaves and flowers
Legumes are easily recognized from the leaves and the flowers. The leaves are usually compound leaves,
often with each leaf divided into 3, 5 or more leaflets. The flower contains 5 sepals and 5 unusual petals
1 large standard petal coming from the back, 2 wing petals at the side and 2 keel petals which may be
joined below. There are 10 or 9 + 1 stamens which are stuck together to form a tube. The fruit is a pod
formed from one carpel which can break into two to let the row of seeds out. The flowers are normally
self-pollinated but they can be cross pollinated by large insects such as bees which can push down the
keel petals and get into the flower.
6.9.16.01 Legumes, Different legumes
1. Winged bean or four angled bean or "as bin" or Goa bean
This should be grown in all school food gardens because the seeds have a high protein content. You can
eat the seeds, green pods, leaves, flowers and tubers.
2. Cowpea, snake bean, yard long bean, lablab bean
These plants are closely related. They are grown for the seeds and pods and as a green manure crop.
3. Peanut or ground nut
They have a high protein content and the plant is a good animal feed. The peanut must be roasted or
boiled before eating.
4. Mung bean or green gram bean
The pods have a high protein content and the seeds can be left to sprout then eaten. The pods are rather
small and students get tired of picking them. It is also a good green manure crop.
5. Soya bean (soy bean)
The seeds are very nutritious but this plant is attacked by lots of diseases in the wet tropics.
6. Chick pea
It has large seeds which are very nutritious.
7. Pigeon pea
Perennial bush which can be used as temporary shade.
8. Other shade trees
The "cocoa shade" albizia, cassia, coral tree, gliricidia, leucaena, poinciana (flame of the forest), wattle.
6.9.16.1 Uses of legumes
You can eat the following parts of the legume plant:
Tender young leaves, e.g. Pigeon Pea
Unripe pods picked when still green or light yellow, e.g. Cowpea
Dried seeds called pulses, e.g. Soya bean, mung bean, pigeon pea
Sprouted seeds, e.g. Mung bean
Tuberous roots, e.g. Winged bean.
6.9.16.2 Legume cover crops
Legumes may be grown between tree crops to cover the soil and stop weeds growing by shading them.
These crops are called cover crops, e.g. the trailing plants, pueraria and centrosema . Erect plants such
as crotalaria and cowpea are grown as green manure. If you dig these plants into the soil at the time of
flowering nitrogen plant nutrient is added to the soil. Some legumes which are trees or shrubs are grown
to provide shade or windbreaks, e.g. leucaena. Legumes which are large trees and have large beautiful
flowers are grown for shade and decoration, e.g. coral tree.
6.9.16.3 History of legumes
Legumes are a very old food. The story in the Bible of Esau and Jacob and the "mess of pottage" refers
to a porridge made of dried legumes called red lentils. In some parts of the Bible it says that legumes are
a food for poor people only. However, when Nebuchadnezzar, King of Babylon, ordered that some of
the children of the Israelites be given some of the King's meat every day, Daniel changed this to more
simple food. After the children had eaten pulses and water for 10 days, they appeared healthier than those
who ate the King's meat.
6.9.16.4 Legumes in the diet
You can use legumes food in 2 main ways:
The unripe green pods and sometimes also the tender green leaves are picked and cooked as a vegetable.
These provide plenty of vitamins if eaten soon after picking.
The pods are picked when almost dry before they split and let the seeds out. They are then dried in the
sun and threshed by putting in a bag and hitting it with a stick. The dried seed called a pulse is stored and
later boiled and eaten. Pulses are an easily digested and nutritious food. They contain about 20% protein,
60% carbohydrates and 3% minerals (especially calcium and phosphorus) and vitamins. The type of
protein is not enough for a balanced diet so some animal protein is still required in the diet. Before
cooking, pulses should be soaked in warm water overnight and the water thrown away. This reduces the
production of gas during digestion. They are cooked by boiling for up to 1 hour.
6.9.16.5 Growth habit of legumes
Legume plants may be erect, spreading, trailing or climbing. The plants usually produce flowers and fruit
over some weeks which require more than one picking. Usually the trailing plants have the longest
harvesting period. Climbing plants save space in the vegetable garden.
6.9.16.6 Planting legumes
Legumes can grow in different types of soils but they should be deeply dug and well drained to allow
roots to grow easily and prevent attacks by fungus and nematode worms in the soil. They are usually
planted towards the end of the rainy season 3 cm deep in rows 50 cm apart between rows and 30 cm
apart within the rows, or planted closer and thinned out to 30 cm.
6.9.16.7 Root nodules
See 9.71: Rhizobium in legumes
Nitrogen fertilizer is not normally needed because the plants can fix nitrogen from the air with their root
nodules. However, if legumes are being grown in a soil for the first time there may not be enough
nitrogen-fixing bacteria, Rhizobium. To provide enough bacteria the seed should be mixed with the
correct type of bacteria just before planting. This is called inoculation. To inoculate, say cowpea seed,
mix the contents of the packet of cowpea inoculant with water and pour it over the seed so they become
evenly coated. Use a Legume Seed Inoculation Chart provided by agricultural chemical companies to
calculate the amount of inoculant for the type and amount of seed, e.g.
Group Used for inoculating Small packet (70 g) Large packet (250 g)
.
 . To treat Kg of seed To treat Kg of seed
Mung Mung bean . 100
Cicer Chick Pea, Cicer 25 100
Centro Centrosema 10 50
Desmodium Desmodium 5 25
Leucaena Leucaena 25 100
Slurry Inoculation
Make a slurry by mixing the contents of the packet with 500 mL water for small packets and 2 000 mL
water for larger packets.
6.9.16.8 Mung bean
See diagram 9.72.1 Mung bean, winged bean, pigeon pea
The crop matures in about 3 months and is harvested over some weeks as the pods ripen. The pods tend
to split so it is best to harvest pale yellow pods in the mornings and let them dry in the sun. They are easy
to thresh by hand to put them in a bag and beat it. The stored bean may be damaged by insects if not
kept dry. Mung bean can be boiled and eaten as a vegetable, or boiled and mashed with sugar or syrup,
or boiled and eaten cold with onion, oil and vinegar. The Mung bean can be sprouted by soaking seeds
and then letting them sprout for 3 to 4 days. Before cooking Mung bean the seeds should be soaked in
warm water overnight and that water thrown away.
6.9.16.9 Cowpea
Cowpea come from Africa and many varieties have been produced, e.g., snake bean or yard long bean
or asparagus bean. Both unripe pods and young leaves are used as a vegetable. The ripe dry seeds are
very nutritious and are easily digested if well cooked. The plants can grow in a wide range of soil types
providing they are well drained. It is an annual leafy plant which can also be used as a cover crop. There
are many different types from erect to trailing and climbing. Flowers are white to purple on long flower
stalks. Pods are smooth and slightly curved and yellow when dry. The seeds may have a dark spot where
it was joined to the pod to give it a "black eye". The colour of the seed is brown to purple. The flowers
are naturally self-pollinating. Seeds of erect varieties should be planted in firm moist seed bed in rows
50 cm between rows and 10 cm within rows. Avoid time of high rainfall and too much fertilizer or the
plants will produce lots of leaves but few pods. Spreading varieties should be planted 30 cm apart and
climbing varieties can be planted in hills 80 cm apart. Weeds should be pulled out by hand-picking when
still young.
There are few diseases and they can be controlled by garden hygiene and rotations. Erect varieties have
a short harvest period and climbing varieties have a longer harvest period and yield a lot more for the area
of garden used. Pods and seeds are easily attacked by fungus diseases in wet weather. The seeds are hard
to store without treating with pesticides.
6.9.16.10 Common bean (haricot bean, kidney bean, French bean, snap bean, field bean)
There are many kinds of these bean which come from Central America. They are grown as a green
vegetable and for the dried seeds. The seeds must be soaked in warm water overnight, the water thrown
away and then well cooked otherwise they cause gas in the intestines. These bean often do not grow
well in coastal areas of the tropics because the high humidity allows them to be attacked by many pests
and diseases. The seeds should be sown in deeply dug well drained soil 3 cm deep, 60 cm apart between
rows, and 10 cm apart within rows. The soil must be loose and fine to allow the stem to lift the cotyledons
easily through the soil. Although they are legumes they need a lot of nitrogen in the soil. Bean are erect
annual plants which mature in 6-8 weeks and can usually be harvested in 2 pickings. They cannot
withstand very hot weather. The seeds store well when dry, especially the red seed varieties. There are
many pests and diseases. Bean fly cause the stems of young plants to split and go brown. Small brown
egg-shaped cocoons can be seen inside the attacked stem. They can be sprayed with Dimethoate, a
dangerous chemical. Bean pod borer is hard to treat because it is a caterpillar which gets inside the pod.
Spider mites cause yellow spots on the leaves in dry weather they can be controlled by Dimethoate.
6.9.16.11 Winged bean ("as bin", Goa bean)
See diagram 9.72.1: Mung bean, winged bean, pigeon pea | See diagram 9.72.4: Winged bean flower
This is a traditional crop in Papua New Guinea. People eat the flowers, young leaves, green pods, dry
seeds and tubers. The dried bean can contain 33% protein and the tubers 10% protein. The plant grows
in almost any type of soil which is well drained. It is a long vine which must be supported on stakes. The
large pods have "wings" on them. Some varieties produce mostly pods and some produce mostly tubers.
Seeds are planted 3 cm deep, 20 cm × 20 cm apart in raised beds or mounds, at the start of the wet
season. They can be interplanted with corn or soybean. Fertilizer and inoculation is not usually needed.
Weeding should be done early to protect the young plants from competition for water. When the crop is
6-8 weeks old stakes or string 2 metres high should be provided to let the plant climb. The main diseases
are leaf spot which can be controlled with Benomyl 50 gram / 100 litres water and soil pests and diseases
which can only be controlled by rotation. Collar rot can only be controlled by shallow planting in
well-drained soils. Flowers, leaves and green pods can be harvested after 3 months and tubers after 5
months.
How to use the winged bean plant as food:
Pods
Winged bean pods are the most popular part of the plant in almost every country where it is grown.
Tender pods may be eaten raw or else chopped and then either boiled in water or coconut milk, or
shallow-fried in oil. The winged bean is also used in soups, and stews. Pods which are too fibrous to eat
whole are often steamed or baked in open fires, and the seeds scraped out and eaten. The seeds may
first be removed and then boiled or fried.
Leaves, shoots and flowers
The growing shoots, young leaves and flowers of the winged bean are edible, nutritious and delicious.
They may be boiled or fried.
Ripe seeds
Winged bean seeds should be soaked until the seed coat starts to soften. They can then be boiled in
water until they are tender, or they may be shallow fried or baked. It is best to soak the seeds in water
beforehand to breakdown some of the toxic substances. The winged bean seed contains about as much
protein and energy as the soybean.
Root tubers
Tubers can be boiled or baked (but not fried) without peeling. The skin then peels off easily. The root
should not be eaten raw.
6.9.17.0 Chemical fertilizers, grade formula
See 12.14.5: Superphosphate production
The grade formula of artificial fertilizers
If the fertilizer contains 13% nitrogen, 13% phosphorus and 21% potassium, 100 grams of the fertilizer
would contain 13 g nitrogen, 13 g phosphorus and 21 g potassium.
The grade formula is NPK =13:13:21.
Other examples of artificial fertilizers are as follows:
muriate of potash (NPK = 0:0:50), superphosphate (NPK = 0:9:0), sulfate of ammonia (NPK = 21:0:0),
urea (NPK = 46:0:0).
The term "potash" applied to mixed fertilizers refers to "K2O equivalent", but not to K2O itself, because
it is not included in a mixed fertilizer.
1. Chemical fertilizers are made in factories. Some are made from minerals which occur naturally and are
later ground to a powder and sometimes treated with chemicals, e.g. ground rock phosphates and
superphosphate. Other fertilizers are chemicals in chemical factories e.g. sulfate of potash (potassium
sulfate). In this topic you will refer to chemical fertilizers as "fertilizers".
2. Some people think that students should not be learning about imported fertilizers. However, many
tropical soils are lacking in certain plant nutrients, e.g. potash, and the use of a small amount of these
fertilizers can greatly increase the yield of the food crops. Imported fertilizers are costly but if they are
used according to the recommendations of the Department of Agriculture and are stored properly they s
should pay for themselves in the increased value of the crop yield. Do some fertilizer trials. Then you can
make your own decision about whether it is cost effective to buy and use imported fertilizers.
3. A good design for a fertilizer trial is as follows:
Block 1 Block 2
Block 3 Block 4
In each block plant 20 cuttings of potato. Blocks 1 and 4 are experimental blocks. Put one teaspoon full
of fertilizer in the soil around each cutting. Blocks 2 and 3 are control blocks, so do not use any fertilizer.
Harvest each block separately and weigh the potato.
Compare the weight of potato from Blocks 1 and 4 with the weight from Blocks 2 and 3. Compare the
value of the harvests if they were sold. Generally speaking, it pays to use fertilizer if the use of fertilizers
can at least double the yield, i.e. weight of blocks (1 + 4) / weight of blocks (2 + 3) / 2.
4. If you use fertilizer you should make a profit.
Profit = (returns from Blocks 1 and 4) to (returns from Blocks 2 and 3) to cost of fertilizer used.
Cost of fertilizer in bags = (cost of fertilizer + freight) × (weight of fertilizer used / weight of whole bag of
fertilizer)
5. The following is an example of a lesson that you could give on chemical fertilizers. You will need a
fertilizer bag. This lesson could be followed by a lessons on how to put fertilizers in the soil.
1. Show the students where chemical fertilizer has been used in your school food gardens, or ask them
whether they have seen it used in a plantation.
2. Show the students a bag of fertilizer. Let them read:
1. the name of the factory which made it, e.g. CFL Consolidated Fertilizers Limited,
2. the weight of the fertilizer, e.g. 50 kg,
3. the grade formula e.g. NPK 12:4:19, tell the students that this means that 100 grams of the fertilizer
contains 12 grams of nitrogen, 4 grams of phosphorus and 19 grams of potassium.
3. Ask the students whether they think it is a good idea to use this imported fertilizer. Ask them to tell you
the advantages and disadvantages of using it.
Advantages:
1. Fertilizer provides plant nutrients.
2. Fertilizer increases the yield and the value of a crop.
Disadvantages:
1. Fertilizer is costly.
2. If fertilizer is not used properly it is wasted.
4. Let the students put some fertilizers in their hands. Do not let them taste it but they can smell it.
6.9.17.1 Fertilizers, straight fertilizers and mixed fertilizers
1. Simple or straight fertilizers contain only one of the main plant nutrients and usually some other plant
nutrient. Single superphosphate contains mainly phosphorus and it also contains some sulfur and calcium.
Muriate of potash contains potassium and chlorine.
2. Mixed fertilizers contain a mixture of simple fertilizers so that nitrogen, phosphorus and potassium may
all be present as well as other plant nutrients. These fertilizers can be mixed before putting them in the soil
or they can be bought already mixed, e.g. "Thrive" and "Zest". Compound (or composite) fertilizers
contain nitrogen, phosphorus and potassium in various forms of chemicals such as ammonium phosphate
nitrate. They also contain other plant nutrients. Some of these are slow release fertilizers such as IBDU
which slowly releases urea into the soil, also "Osmocote" which slowly releases an NPK mixture.
2. Some fertilizers have high concentrations of plant nutrients and are called high analysis fertilizers,
e.g. triple superphosphate. Some fertilizers are made in the factory as granules or pellets. They give plants
the correct mixture of plant nutrients at all times and are thus better than mixtures.
3. The contents of fertilizers are shown by a grade formula which uses the chemical symbols of the
primary plant nutrients NPK. This is used in two ways, e.g. The old way listed the contents of potassium
and phosphorus as their oxides. If the fertilizer contains:
Previous formula - Current formula -
13% Nitrogen N 13% Nitrogen N
13% Phosphorous Oxide P2O5 13% Phosphorus P
21% Potash K2O equivalent 13% Potassium K
4. Previous formula
100 g fertilizer contains 13 g Nitrogen, 13 g Phosphorus Oxide and 21 g Potash (Potassium Oxide).
The fertilizer would be shown as: NPK = 13:13:21.
5. Current formula
The current formula lists the contents as the elements nitrogen, phosphorus and potassium.
If the fertilizer contains 13% Nitrogen N 13%, Phosphorus P 21%, and Potassium K, this means that 100
grams of the fertilizer would contain 13 g nitrogen, 13 g phosphorus and 21 g potassium.
The fertilizer is shown as NPK =13:13:21.
Some examples of grade formulae:
.
 NPK
previous formula %		 NPK
previous formula %		 NPK
previous formula %		 NPK
current formula %		 NPK
current formula %		 NPK
current formula %
.
 N P2O5 K2O N P K
Muriate of potash 0 0 60 0 0 50
Superphosphate 0 22 0 0 9 0
Sulfate of ammonia 21 0 0 21 0 0
Triple superphosphate 0 47 0 0 20 0
Urea 46 0 0 46 0 0
Fertilizers containing a high concentration of plant nutrients and are called high analysis fertilizers,
e.g. triple superphosphate. Some fertilizers are manufactured as granules or pellets that give the correct
mixture of plant nutrients at all times and so are better than mixtures.
6. There are 4 methods of adding fertilizer to the soil:
6.1 Broadcasting
The fertilizer is spread over the surface of the soil by hand or by machine. It should then be dug into the
soil using a hoe or plough because if left on the surface nitrogen plant nutrient may be lost as ammonia gas.
Fertilizer dug into the soil about 2 weeks before the crop is sown is called a base dressing.
6.2 Banding
The fertilizer is placed below the surface of the soil by hand or by machine. A furrow is dug between the
rows of seeds at a depth of about 2 cm deeper than the seeds, the soil is then turned to cover the band of
fertilizer. Banding is done at about the same time as the seed is sown.
6.3 Top dressing
The fertilizer is spread after the crop has been sown. This is usually done with nitrogen fertilizer to provide
extra plant nutrient at certain times to make more shoots and leaves. However, nitrogen plant nutrient may
be easily washed out of the soil so it is best to add some of the fertilizer by banding at sowing time and
add the rest by top dressing when the shoots and leaves are growing.
6.4 Side dressing
The fertilizer is placed between the rows by banding or placed under the plants and watered in after the
crop has been growing for some time. This is done for maize (corn) vine crops and tree crops to increase
the yield of fruit.
7. Straight fertilizers, simple fertilizers, NPKS
Common name Chemical formula Approximate composition
Nitrogen fertilizers . .
Sulfate of ammonia (ammonium sulfate) (NH4)2SO4 21% N and 24% S
Nitrate of potash (potassium nitrate) KNO3 38% K and 13% N
Nitrate of soda (sodium nitrate) NaNO3 16% N
Urea CO(NH2)2 46% N
Phosphorous Fertilizers . .
Single superphosphate Ca(H2P04)2 + CaSO4 0.9% P, 10% S, 20% Ca
Triple superphosphate Ca(H2PO4)2 19% P, 02% S, 16% Ca
"Special" superphosphate . Superphosphate + Copper or Zinc or Molybdenum or sulfur.
Potash Fertilizers Any of: potassium chloride, potassium sulfate, potassium magnesium sulfate, potassium nitrate. (but not potassium oxide) .
Muriate of potash (Potassium chloride) KCl 50% K
Sulfate of potash (Potassium sulfate) K2SO4 40% K and 16% S
Other Straight Fertilizers . .
Sulfur S 99% S
Gypsum CaSO4.2H2O 18% Ca and 14% S
8. Mixed or compound fertilizers
They have many different compositions, e.g. 12% N, 4% P, 19% K, 10% S (high in potassium and sulfur),
12% N, 14% P, 10% K, 3% S (high in phosphorus).
Osmocote is made with many different compositions but IBDU contains 33% Nitrogen. Only certain
forms of nitrogen fertilizer are suitable for controlled release in the tropics. Most dump their nitrogen.
The estimated lasting period of 0.7 to 2.6 mm granules of IBDU depends on pH, water holding capacity
of the soil and temperature.
6.9.17.2 Soil acidity
See 5.19: Acid soils and alkaline soils
The acidity of a soil is measured by the pH scale. Numbers are used after pH to show whether the soil is
acid or alkaline:
pH pH pH pH pH pH pH pH pH pH pH pH pH pH
1 2 3 4 5 6 7 8 9 10 11 12 13 14
(pH 1-2 very strongly acid, pH 5-6 weakly acid, pH 7 neutral, pH 8-9 weakly alkaline,
pH 13-14 very strongly alkaline)
In pure water, the number of H+ ions = the number of OH- ions, so water is neutral. In an acid soil there
are many more H+ ions than OH- ions. In alkaline soils there are more OH- ions than H+ ions. When a
chemical fertilizer is added to a soil, it dissolves in the soil water and breaks up into positive ions and
negative ions like the water molecule. For example when muriate of potash fertilizer, which is potassium
chloride, is put in the soil, it adds to the soil potassium ions, K+ and chloride ions, Cl-. These ions become
attached to the clay particles and organic matter particles in the soil. However, if the soil is too acid or too
alkaline, the large number of H+ ions or OH- ions will interfere with the attachment of fertilizer ions to soil
particles. They may cause the fertilizer ions to be held too strongly to the soil particles. If this happens,
the nutrient ions cannot be used by the roots of plants and you say that the nutrients are unavailable to the
plants. For example if the soil is too acid, calcium, magnesium, potassium, sulfur and nitrogen are not very
available to plants. If the soil is too alkaline, iron, manganese and aluminium are not available to plants.
Copper and zinc are not available when the soil is too acid or too alkaline. If the fertilizer ions are held too
weakly to the soil particles, then they will be easily washed out of the soil by heavy rain, and will be lost to
plants. So if you want to use fertilizers properly, it is best if you can make sure that your soil is slightly acid
but not strongly acid or strongly alkaline. If the soil is too alkaline, then many plant nutrients like iron,
manganese, boron, copper and zinc will not be very available to plants. It is a good idea to use the fertilizer
mixtures recommended by the Department of Agriculture. It only pays to use imported fertilizers if the
plants use it to increase the amount of food they produce. Do not use the wrong mixed fertilizer,
e.g. if you use a mixed fertilizer high in nitrogen on potato, it will only form a lot of leaves and little tubers.
Commercial soil pH test kit
1. For the best growth of plants it is essential that the acidity (measured by pH) of the potting mix or soil
is suitable for the plants you want to grow
2. Most soils are either slightly acid or slightly alkaline. A few soils are neutral (between acid and alkaline).
Some soils are very acid and some are very alkaline.
Neutral soils have a pH of 7. Acid soils have pH values < 7. Alkaline soils have pH > 7.
3. Plant growth is affected by soil pH. Few plants grow well in soils with pH values below 4.5. Plants
from very acid soils grow best in soils of pH 4.5 to about pH 6, but do not grow well on neutral and
alkaline soils. Most other plants grow best in soils of pH values 6 to 7.
Plants from alkaline soils will grow on slightly acid soils, but they will also grow well on alkaline soils.
4. Most plants grow well in potting mixes when the pH of the mix is in the range 5.5 to 6.5.
Plants from very acid soils prefer a potting mix with a pH in the range 4.5 to 5.5.
5. Plants adapted to acid soils are often unable to get enough of the essential nutrients iron and manganese
from alkaline soils. Their young leaves show yellowing (chlorosis) and growth is poor. Severe deficiency
leads to death. By contrast, plants adapted to alkaline and slightly acid soils can be harmed by the
amounts of dissolved aluminium and manganese present in very acid soils. They probably cannot take up
enough of the essential element calcium.
6. Raise soil pH by adding agricultural lime or dolomite. A 1:1 mixture of the two may be best.
Lime / dolomite (g / m2), To raise pH of the top 10 cm about 1 pH unit.
Soil type Lime / dolomite (g / m2)
Sands 100
Loam 200
Clay soils 300 to 400
Organic soils 600
Lower the pH of slightly alkaline soils (pH below 7.5) with agricultural sulfur.
Sulfur (g / m2) To lower pH of the top 10 cm by about 1 pH unit.
Soil type Sulfur (g / m2)
Sands 25
Loam 50 to 70
Clays 100
7. The large amounts of solid lime often present in alkaline soils with pH values higher than about 7.5
make it almost impossible to make these soils acid.
8. You can change potting mix pH. The mix must be moist enough to use for potting.
Raise pH with dolomite. Add 1 to 1.5 g/L of mix to raise pH by about one unit.
Lower pH with sulfur. Add 0.3 g/L to lower pH by about one unit.
Check the pH again after two weeks storage and add more as needed.
9. The pH of mix in pots should be checked every few months, because most fertilizers produce acidity.
Raise pH with a suspension of hydrated lime (builders' lime). Suspend 5g (a heaped teaspoon) in a litre of
water. Pour the suspension onto the mix in the pot. Use 200 mL for each litre of the mix. (A 130 mm pot
contains about 1 litre of mix.) You should pot plants again if the pH of the mix is below 4.5.
Lower pH with a solution containing 2 g of iron sulfate per litre of water. Apply 200 mL per litre of mix
and within two minutes heavily water the pot to remove excess salt. Wait for one week, check mix pH
and add more iron sulfate if needed.
10. Preferred pH ranges
1. Soils of pH 4.5 to 6 potting mixes of pH 4.5 to 5.5
Camellia, Rhododendrons, Azalea, Gardenia, Erica, Macadamia, Juniper, Spruce, Japanese Maple
2. Soils of pH 5.8 to 7.5 potting mixes of pH 5.3 to 6.5
Most vegetables, bedding plants, commonly grown shrubs and trees.
3. Soils of pH 7 and higher potting mixes of pH 6 to 6.7
Many cacti and succulents. Plants native to arid areas.
Grow roses and citrus that have been grafted onto rootstocks that tolerate these soils.
11. Directions for using the colour chart for soil pH
Careful sampling is essential. For a garden bed, take at least 5 samples from holes dug in different parts
of the bed. Each sample is to extend from the surface to a depth of 10 cm. Test each sample separately.
For farm paddocks, take at least 20 samples from each area. Mix samples together thoroughly and test
as one sample. For bought and home made potting mix, thoroughly mix the bulk lot.
For mix in a pot, first knock the root ball from the pot. Remove a wedge of mix representing the whole
depth of the root ball. Mix thoroughly. For a mix in large tubs, dig down the side of the root ball as
deeply as is possible. Thoroughly mix the sample removed.
12. Measure pH
Place a level teaspoon of mixed soil or potting mix on the test plate. Add 3 to 5 drops of indicator liquid
and stir with the rod provided. Dust the paste with the white powder provided. Wait one minute. Read
from the colour card the pH value of the colour nearest to that of the sample. The test kit contains one
bottle of pH Dye Indicator and one bottle of barium sulfate solution.
The test kit is manufactured in Australia by Manutec Pty. Ltd., 30 Jonal Drive, Cavan, South Australia
5094, Australia.
6.9.18.0 Pesticides
1. Do not attempt to teach lessons on this until you have carefully read the following section on Resource
Material on pesticides.
2. Do not teach this lesson until you have shown students how to use the spray using water only. These
notes will show you how to teach lessons on insecticides if you want to spray your hibiscus cabbage
(aibika or bele or pele) plants because they are badly attacked by leaf miners.
3. The main aim of these lessons is to teach students how to use carbaryl insecticide safely. You will need
insecticide concentrate, a sprayer, a plastic bowl and mixing stick, a 5 g measure and 4 L of clean water.
Method
1. Show students the damage done by the leaf miners to aibika or bele. Tell the students that you do not
like to use pesticides, but in this case you must use a pesticide because it is the only way to save your
aibika or bele crop.
2. Show the students the tin of concentrate. Let them read the label. Note the name of the company
which makes the insecticide, the trade name of the chemical, the common chemical name, the weight of
the contents.
3. Now let the students read from the label: "for the control of caterpillars, plant bugs, leaf-eating beetles
and earwigs". Ask them whether this is the right insecticide for the job.
4. Read out to the students from the label. "This concentrate is dangerous if swallowed, breathed in or
absorbed through the skin." Tell them what to do if these accidents happen.
5. Read the instructions: "apply 5 Grams in 4 litres of water". Show the students how you will measure 5
grams of the powder and how you will measure 4 litres of clean water.
6. Read the mixing instructions. "Mix the required amount of insecticide with a small quantity of water to
form a cream and pour into remainder of the water.
7. Measure out 5 grams of the powder into a plastic bowl, use some of the measured 4 litres of water to
make a smooth paste, pour about 2 litres of water into the spray, pour the insecticide paste from the bowl
into the sprayer, use some water from your original 4 litres to wash out the plastic bowl and pour that into
the sprayer, put the rest of the 4 litres of water into the sprayer, close the sprayer tightly and shake it.
8. Tell the students to remember:
1. what to read on the insecticide tin,
2. how to make up the spray. In the next lesson, you can show them how to use this spray.
Resource material to Pesticides
Use only the procedures, agricultural chemicals and insecticides recommended by the local field officer
of the Ministry of Agriculture.
6.9.18.1 Caution before using pesticides
You must read these notes!
1. Pesticides are chemicals which can kill living things which attack plants and animals. There are different
kinds of pesticide:
1.1 Insecticide kills insects, Fungicide kills fungus and sometimes bacteria,
1.2 Miticide or acaricide kills mites and spiders,
1.3 Nematicide kills nematode worms,
1.4 Molluscicide kills slugs and snails,
1.5 Rodenticide kills mice and rats,
1.6. Herbicide or weedicide kills weeds.
2. Do not use any pesticides which are not mentioned in this chapter. All pesticides are dangerous to
humans, especially children, so they must be used and stored with great care if they are used in school
food gardening. Use pesticides only if there is no other way of saving your crop. If you want to use
pesticides always tell the headmaster what you intend to do.
3. The rules for using pesticides are as follows:
1. Read the directions on the container before opening. Make sure that you have the right pesticide for
the particular pest. Make sure that you understand how much pesticide to use. Make sure that your
sprayer and tank is clean and working. Try it out with water first.
2. Do not breathe in pesticide or spill it on your skin don't smoke or eat when using pesticides. If you
spill pesticide on your skin wash it off with plenty of soap and water straight away.
3. Wear special protective clothing and wash yourself after spraying. Always handle concentrates with
rubber gloves which you keep for that purpose only. Wear a work shirt buttoned down to the wrists, long
trousers and boots.
4. Spray on a calm day.
5. After spraying dig a hole in the bush and pour down it any makeup spray left in the tank. Wash out the
sprayer and pump and pour the washing water down the hole.
6. Store the unused pesticides in a safe place where children cannot enter. Always use the old container,
do not store in a new container such as a drink bottle. Do not store pesticides near food.
4. The pesticide you will buy will often be in a concentrated form so you must follow a proper mixing
procedure. Always use a plastic measuring cylinder or the special measure some pesticide factories make
so you do not guess amounts of pesticide. Dusts are blown or sprinkled onto plants without using water.
5. Mixing procedure for a liquid pesticide:
1. Fill sprayer tank half way with water.
2. Add measured amount of chemical to sprayer.
3. Fill sprayer tank with water.
4. Shake the sprayer
6. Mixing procedure for a powder pesticide:
1. Put small quantity of water in bucket.
2. Put measured quantity of pesticide powder on top of water, leave till it is thoroughly wetted and then
mix into a paste.
3. Add water, then add to half filled knapsack as per instructions for liquid pesticides. If this is not done,
some wettable powder will go lumpy and give mixing problems.
6.9.18.2 Dusts
Dusts are best applied either in a proper duster or a tin with a stocking over the end.
6.9.18.3 Withholding period
This is the recommended time between spraying the crop and harvesting the crop so that people will not
be made sick by eating the pesticide still on the plants. Make sure that crops which have been sprayed
are not harvested within the withholding period. A crop must be washed thoroughly before being eaten.
6.9.18.4 Active constituent
Pesticides are usually a mixture of chemicals. The chemical which kills the pest is called the active
constituent (or common chemical name). The other chemicals in the pesticide just make it easier to use
and are called the inert ingredients. Some active constituents are inorganic compounds, such as copper
oxychloride and some are organic compounds which are compounds of carbon. Thus an organic chloride
compound contains a carbon compound and chlorine, and an organic phosphate compound contains a
carbon compound and phosphorus The name of the active constituent is always written on the label.
Pesticides are made by many different factories in different countries and each factory gives the pesticide
its own special name called a trade name, e.g., XXXX or ZZZZ both contain carbaryl. So it is possible
or pesticides with different names to contain the same active constituent and be used to kill the same pests.
6.9.18.5 Resistance to pesticides
It often happens that pesticides do not kill all the pests some get sick but still live. These pests may
produce offspring which will not be affected by the pesticide to you say that these pests have developed
resistance to this pesticide. For this reason it is not wise to always use the same pesticide. Instead the
pesticides should be changed from time to time. So when you use all of one pesticide, try using another
type.
6.9.18.6 Persistence
Some pesticides and weedicides remain active for a long time, even in the soil. The time they remain
active is called "persistence". Pesticides that persist for a long time may be dangerous because their
poisonous properties may affect later insects, animals and crops.
6.9.18.7 Surface acting agents
Surface acting agents are chemicals which may already be added to the pesticide or which you should
add to the pesticide. They include detergents, soaps, wetting agents, spreaders and stickers. These
chemicals spread the pesticide over the plants better and may make them stick to the plants. The label on
the pesticide will tell you whether to mix with surface active agents which are sometimes called a
surfactant. There are many trade names of surface active agents or you can use any detergent used for
washing.
6.9.18.8 Emulsifying agents
An emulsifying agent is a chemical similar to soap which helps oil and water to mix and form an emulsion.
When two liquids can mix they are called miscible. Wettable powders (W.P.) are a mixture of an active
constituent such as sulfur, an emulsifying agent, and inert materials such as clay. Water is mixed with the
wettable powder to make a spray solution. Emulsifiable concentrates (E.C.) are a mixture of active
constituent, an emulsifying agent, and oil. Water is mixed with the emulsifiable concentrate (E.C.) to make
a spray solution. Emulsifiable concentrates and wettable powders should never be mixed together. The
label on the pesticide tell you which other pesticides can be mixed with it.
6.9.18.9 Granules
Synergists. piperonyl butoxide
Granules are very small pieces of rock with pesticides stuck to them. They are usually used when the
pesticide has to be put in the soil. Fumigants are poisonous gases used to kill pests in stored crops or
soil. They are very dangerous and should not be used in schools. Some Departments of Agriculture use
the dangerous poison ethylene dibromide on agricultural products which may carry disease. Synergists
are chemicals added to pesticides to make them more poisonous, e.g. piperonyl butoxide makes the
insecticide pyrethrum more poisonous. W / V This means weight per volume or the weight of active
constituents in a certain volume of pesticide. So 30% W / V emulsifiable concentrate means 30 grams of
active constituent in every 100 mL of the emulsifiable concentrate. This may also be written as 300 g / L
(grams per litre). W / W. This means weight per weight or the weight of active constituents in a certain
weight of pesticide. So a 50% W / W wettable powder means 50 grams of active constituent in every
100 grams of wettable powder. This may also be written as 500 g / kg (grams per kilogram).
6.9.18.10 Pesticide safety
1. Toxic means poisonous to humans.
2. Safe pesticides: Benomyl, Mancozeb, Maneb, Methoxychlor, Quintozene, sulfur, Zineb.
3. Fairly safe pesticides: Harmful, they may cause sore eyes, nose, throat or skin, but there is not much
danger if you are careful not to touch or breathe the pesticide.
4. Do not allow students to use Carbaryl, Malathion or Trichlorophon.
5. Dangerous pesticides, toxic.
If these pesticides are breathed in or left on the skin for some time you may get sick and die. Only
experienced teachers should use these poisons, e.g. Paraquat, Naled, Rotenone, Nicotine, Dimethoate,
Methiocarb. Some pesticides are dangerous if swallowed but not dangerous if left on the skin.
6.9.18.11 Pesticide safety, FIRST AID
If any person gets ill who has been using a pesticide, he should be taken to a doctor or hospital straight
away. Tell the doctor or hospital the name of the pesticide used (active constituent) and show him the
container. The person who is sick from pesticide should be left to rest, clothing should be changed and
the whole body washed. He may need artificial respiration if his breathing stops. If a person has drunk
the pesticide he should be given an emetic. This will make him vomit. A good emetic is 2 tablespoons of
salt in warm water, then push the handle of the spoon gently on the back of the tongue. He should be
kept head down, face down. Give the person Ipecac syrup if it is available. Do not give the person
alcohol. Pesticides on the skin should be washed off with plenty of soap and water, keep washing for a
long time.
6.9.18.12 Insecticide types - contact, ingestion, systemic
1. Most insecticides kill insects by attacking the nervous system. These chemicals can also harm humans,
especially children, so they must be used and stored with great care when used in school food gardening.
2. Insects can take in insecticides in 3 ways:
1. Contact poison
The insecticide touches the body of the insect which then absorbs it.
2. Ingestion or stomach poisons
The insecticide is sprayed onto plants and the insects eat the plants.
3. Systemic poison
The insecticide is sprayed onto plants which absorb it into the sap, sap sucking insects then suck up
insecticide in the sap. However, most insecticides are taken in by more than one way. Remember that
insecticides may kill the good insects such as bees as well as the bad insects which eat your crops.
So use insecticides only when you cannot control the bad insects any other way. If the bad insects are not
doing much damage to your crops then do not use insecticides.
6.9.19.0 Sprayers and dusters
1. The chemicals used in agriculture may be applied as granules, dusts, or sprays. Granules are usually
put into the soil, dusts are blown onto the crops and so do not need water, but sprays must be made up
by mixing the chemical concentrate with water and sometimes a wetting agent. Granules can be spread by
hand or you can buy a granule applicator or spreader. The cheapest dusters are the plunger type which l
look like a bicycle pump. There are also larger and dearer rotary hand dusters. The simplest duster is
made by cutting the bottom out of an opened fish tin and then put it in an old sock.
2. There are 3 types of sprayers:
1. Slide action sprayers
They are the cheapest. They are similar to the common fly spray. They contain up to 5 litres of spray.
It is very tiring to use them for a long time. They do not control the pressure of the spray. These sprayers
can be used in school kitchen gardens.
2. Continuously pumped knapsack sprayers
They are worn on the back or over the shoulder. They should give a continuous spray if you pump them
slowly and evenly. They usually contain 10-15 litres of spray. They may be made of brass or plastic.
Brass sprayers are tough but heavy. Plastic sprayers are light but can be damaged if dropped or left out
in the sun. Plastic knapsack sprayers are the best type to use in school field gardens.
3. Compression type sprayers
After filling these sprayers, they are pumped up to a high pressure. Then they can be used without further
pumping. These sprayers are probably too expensive for schools.
3. Care and maintenance for a knapsack sprayer
1. Wash out the sprayer tank, hose and nozzle with clean water.
2. Clean the jet which is the little hole at the end of the nozzle which the spray passes through. Check that
it is the right sire for the job. Be very careful not to lose this little jet.
3. Read the instructions on the chemical container carefully. Then measure out the amount of chemical
you need for the job.
4. Add clean water to the sprayer until it is half full.
5. Put the measured amount of chemical into the sprayer. Use a special chemical measure or a graduated
cylinder to do not guess the amount of chemical concentrate. 6. Wash the chemical measure and put this
water into the sprayer. Then fill the sprayer with water.
6. Do not spray in the wind or rain.
7. When spraying walk evenly at about one pace each second. Give each plant an even covering.
8. When finished, dig a hole in the bush and tip out all the unused spray into it. Wash out the sprayer,
hose and nozzle and tip all this water down the hole. Remove the hose and nozzle then hang them upside
down on the wall inside a lock up shed.
Method
1. Do not use real chemical, use clean water instead!
2. Show the students a knapsack sprayer containing water. Briefly spray some plants with it so that all
students know what it is used for.
3. Tell the students that this is a knapsack sprayer which is used to spray plants with chemicals which will
kill insect pests and disease. Tell them that they must look after the sprayer very carefully because it is
expensive, it is easily broken and it is used to spray poisons.
4. Let the students look closely at the sprayer and pick it up. Ask them the following questions:
1. What is the name of the company which made the sprayer? [XXXX or ZZZZ]
2. Ask students to point to the tank, pump, pump handle, hose, nozzle, jet, harness.
3. How much spray can you put in the tank. [e.g. 13.6 litres or 16 litres]
4. What is the tank made of? [e.g. brass or plastic (polythene)]
5. Demonstrate the first 8 steps of looking after a knapsack sprayer as set out in the manual.
1. Let each student do some spraying. Remember to even pumping, steady walk, wet all of plants evenly
(including underside of leaves).
2. The students must NOT spray other people with the spray because the chemicals in sprays are poisons.
3. Demonstrates steps 9 and 10 of looking after a knapsack sprayer.
6.9.20.0 Understanding the records
Preparation
1. Record books such as the School Food Gardens Diary, Production Record Book and Receipt Book
should be written up each day when something occurs.
2. The Cash Receipts Journal and Cash Payments Journal should be written up at the end of each week.
3. At certain times you should read all these records again so that you can remember and think about all
the information about each crop and about the school food gardens as a whole. You should do this when
each crop has been harvested and eaten or sold at the end of a period such as a term or a school year
when it is convenient to think about the school food gardens as a whole. Read all these records again to
improve your knowledge about the school food gardens and to assist in further planning.
4.0 Collect 3 type of information, Yields, Profits, Comparative yields
4.1 Yields
Get this information from your Productions Record Book. The information you will need are as follows:
1. Yield of each crop in kilograms per hectare (kg per ha) (or yield on a smaller area).
2. Yields of kitchen gardens in kilograms per garden
3. Yields of trial gardens. e.g. single cropping (potato) and intercropping (potato and corn) and also crops
with fertilizer and crops without fertilizer.
4. Yield of each crop as income (returns) per hectare. How much money was received for each hectare
or smaller area of the crop or for each kitchen garden.
5. Yield of each crop as kilograms per hectare divided by total number of student hours worked to
produce that yield.
6. Yield of each crop as income per hectare divided by the total number of student- hours worked to
produce that yield, i.e. kilograms per hectare per student hour worked.
You can calculate yields in other ways that may be useful for further planning e.g. yields as the number of
school meals per hectare.
Yield per hectare of all the school food gardens together for one year. This is called the productivity of the
school food gardens.
4.2 Profits
The second type of information you should be collecting is on profits.
1. "Returns" refers to the money you receive for a crop.
2. "Costs" refers to the money you pay for things to produce the crop. Costs are divided into production
costs and establishment costs.
3. "Production costs" refers to the costs of items used in producing a crop, e.g. seeds, fertilizer,
insecticide, tractor hire and cost of paid labour. Production costs include cost of planting material bought,
cost of tractor hire, cost of fertilizer used, cost of insecticide used.
4. "Establishment costs" refers to the cost of items needed to produce the crop but which last a long time
and can be used to produce other crops e.g. nursery, tools, fencing materials, buildings. For a lettuce
project a special nursery had to be built for the lettuce seedlings so you may include this establishment
cost for this crop when calculating the profit of the lettuce project. Assume that items of establishment
costs will last for 5 years. So for any one year, divide the establishment costs by 5.
Profit is the amount of money left when you take costs away from returns.
Profit = Returns to Production Costs to Establishment cost / 5
Try to calculate the profit for each agricultural project in your school food garden. This is fairly easy to do
for a project such as a chicken project because the materials you have to buy for it cannot usually be
used for anything else. However, this is not so easy if you want to find the profit of separate crops.
For example, how do you find the establishment cost to a potato project of a fence dividing it from other
crops?
How do you find the establishment cost of tools which are used on many projects and on general school
maintenance?
These costs can be found when you work out the profit of all the school food gardens over a year but it is
best to ignore them when finding the profit of individual crops unless only that crop uses the item.
At the end of the term or school year you can calculate the profit of all the school food gardens together.
In this case you can include items such as cost of fences, tools, machinery and buildings in the
establishment costs. You should be careful not to compare the profits from school food garden as a whole
with those of real farms because there are important differences between the two so you cannot find the
profit in the same way. A farm will have more costs than a school e.g. taxation, rent, cost of labour. You
can borrow things for use in the school food garden from the rest of the school which the farmer would
have to pay for e.g. cost of electricity, use of school tractor, use of measuring tape from the maths
department. You can even borrow things from the Department of Agriculture. In a school you have lots
of free labour for short periods of time but the labour is not efficient because you are using children.
In a farm you would employ fewer labourers for whole days and the labour is more efficient.
School projects are often too small to make a real profit. The cost of fencing alone may make small
cattle or chicken projects unprofitable. Not many schools can use a tractor enough to make this purchase
lead to profitable projects.
4.3 Comparative yields
You should be able to compare the yield of your crops so that you can decide whether it is better to grow
potato or cassava, or is it better to grow wing bean or cowpea? You can calculate and compare yields as:
1. Kilograms per hectare (kg / ha)
2. Kilograms per hectare per student hour worked,
3. Meals per hectare or meals per kitchen garden.
With the above information and a knowledge of rotations you should be able to decide which crops to
plant first.
1. Explain the meaning of returns, costs and profit. Tell the students why you should always calculate the
profit of a vegetable project.
2. Let the students fill in this table using your records:
2.1 Returns $.
2.2 Production costs $
2.3 Seeds $
2.4 Fertilizer $
3. Establishment costs $
If you assume that the items will last 5 years then for any one year divide the establishment costs by 5.
3.1. Nursery $
3.2 Miscellaneous, plastic bags $
4. The students can now calculate the profit of this project.
Profit = [Returns - Production costs - (Establishment costs / 5)]
5. Ask the students to suggest what can be done with the profits. They can be used to buy things you
need such as food and clothing. They can also be used to buy things you need for new projects,
e.g. buy more seed and fertilizer. This is called investing. Tell them that it is not good to spend all the
profits on things you need. Some of the profits should be kept for investing in new projects.
6.9.15.4 Boron deficiency
Boron deficiency is uncommon but may occur in areas of high rainfall and leached soils. Also, boron may
be present in the soil but is not available in soils with a high pH especially in wet seasons. The primary
role of boron is its involvement in the stabilization of the primary cell walls in plant cells. Boron is also
involved in the carbohydrate metabolism in plants, protein synthesis, seed and cell wall formation,
germination of pollen grains and growth of pollen tubes and sugar translocation. Boron is important for
cell division and for development in the growth regions of the plant near the tips of shoots and roots. It
also affects sugar transport and may be associated with some functions of calcium. Boron affects
pollination and the development of viable seeds that, in turn, affect the normal development of fruit.
Some boron is needed for the plant to use calcium. The effects of deficiency appear first in young tissues,
growing points, root tips, young leaves and developing fruit. Boron is more readily leached than other
trace elements especially from acid sandy soils or the highly weathered red basaltic soils. Heavy leaching
rainfall can remove much of the available boron from the surface soil. Drought or cool spring or autumn
soil temperatures can reduce the root's access to boron and capacity to absorb soil boron. Since fruit
crops require a small but continuous supply from the soil for growth, pollination and fruit development,
a deficiency of boron can be induced by fluctuating seasonal conditions. So symptoms may suddenly
appear in one season though the problem has not been seen for some years. High levels of exchangeable
aluminium, over-liming, excessive irrigation, heavy application of potassium or nitrate fertilizers, and
practices that lead to root damage or soil compaction can induce boron deficiency. Loss of soil organic
matter under orchard culture also reduces the capacity of soils to retain boron in older orchards.
Symptoms may affect fruit, shoots, and leaf growth but unless the deficiency is severe the symptoms in the
fruit are usually noticed first. Recommended foliar spray is 150 g / 100 L polyborate powder
(20.5% Boron). Soil application of 20 - 30 kg / hectare suit most crops and soils including bananas and
pineapples but the rate for papaya should be < 20 kg / hectare. Excess boron is highly toxic to plants so
when applying the borax to the soil spread it evenly over the area and crush all lumps to avoid high
concentration hot spots. Polyborate fertilizer at half the borax rate can be dissolved in water and sprayed
onto the soil. A spray of 1 g borax dissolved in a cup of hot water and 1 g urea or urine in 1 litre of water
sprayed at early flower bud stage increase fruit set.
6.9.15.5 Tests for adding gypsum to the soil
Gypsum may improve the structure of soils that are slippery and sticky when wet, tend to slump and get
very muddy during rain, form a crust on drying, allow only slow entry of water, do not break into anything
smaller than large clods during digging. To test whether a soil may benefit from gypsum, drop a 5 mm
diameter crumb of dry soil aggregate into a beaker of deionized water.
Place a similar sample of the soil in the palm of one hand, add deionized water and knead the soil until all
of the lumps have been broken up. Squeeze some kneaded soil into an aggregate about 5 mm in diameter
and drop it into a second beaker of water. Observe the beaker for an hour and again after 24 hours. Some
aggregates remain unchanged, even after 24 hours. Some aggregates fall apart during the first hour, but the
smaller aggregates so formed remain where they fall. Other aggregates slowly disperse into the water,
whether they fall apart or not. A surrounding "halo" of clay particles forms around the aggregate then
spreads to form a cloudiness in the water. Gypsum will not improve the structure of a soil where the
aggregates remain unchanged or fall apart without dispersion. The more cloudy the water, and the more
rapidly the cloudiness develops, the greater will be the benefit of adding gypsum to the soil, and the more
gypsum will be needed. Use 0.5 - 1 kg of gypsum per square metre. Beside improving the structure of the
soil, gypsum is a good source of calcium and does not change the pH of the soil.