Foodgardens3

School Science Lessons
School food gardens for tropical regions
Updated: 2008-03-15
Please send comments to: J.Elfick@uq.edu.au
See also: Interesting Websites
Biology names

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
See also: Names of plants and fungi
6.9.15.0 Fertilizing the soil
6.9.15.1 Plant nutrients
6.9.15.2 Green manure
6.9.15.3 Liquid manure
6.9.16.0 Legumes
6.9.16.1 Uses of legumes
6.9.16.2 Cover crops
6.9.16.3 History of legumes
6.9.16.4 Legumes in the diet
6.9.16.5 Growth habit of legumes
6.9.16.6 Planting legumes
6.9.16.7 Root nodules
6.9.16.8 Mung bean (Phaseolus aureus)
6.9.16.9 Cowpea (Vigna unguiculata)
6.9.16.10 Common bean (Phaseolus vulgaris)
6.9.16.11 Winged bean (Psophocarpus tetrogonolobus)
6.9.17.0 Chemical fertilizers
6.9.17.1 Two types of fertilizer
6.9.17.2 Common fertilizers
6.9.17.3 Mixed or compound fertilizers
6.9.17.4 Plant nutrients
6.9.17 5 Acidity and alkalinity
6.9.17.6 Soil acidity
6.9.18.0 Pesticides
6.9.18.1 Caution before using pesticides
6.9.18.2 Dusts
6.9.18.3 Withholding period
6.9.18.4 Active constituent
6.9.18.5 Resistance to pesticides
6.9.18.6 Persistence
6.9.18.7 Surface acting agents
6.9.18.8 Emulsifying agents
6.9.18.9 Granules
6.9.18.10 Pesticide safety
6.9.18.11 First Aid
6.9.18.12 Types of insecticides
16.13.0 Pesticides and herbicides
6.9.19.0 Sprayers and dusters
6.9.20.0 Understanding the records

6.9.15.0 Fertilizing the soil
Preparation
This topic is concerned with why you must fertilize the soil and the different ways of fertilizing.
School food gardens have only a limited area and the amount of physical effort is limited by the size of them, the time available and how much physical activity you think is reasonable to expect from students. So it is important to have a maximum use of all kinds of fertilizers to make the school food gardens as productive as possible.
The following lesson is based on the resource material at the end of the lesson.
Method
1. Show the students some grey white plant ash or heat some plant material very strongly until only grey white ash remains. Let the students taste this ash. It tastes salty. Tell them that they are tasting some of the plant nutrients which are chemicals that the plants take in from the soil. Tell them that all plants need plant nutrients and that if there are not enough of the right plant nutrients in the soil then you must put some in the soil. Putting plant nutrients in the soil is called "fertilizing" the soil.
2. Fertilizing the soil means to add extra plant nutrients to the soil so that the plants will grow better.
3. There are 4 reason for fertilizing the soil.
3.1 The rock the soil was made from did not have enough plant nutrients in it.
3.2 Soil loses plant nutrients when water washes through it.
3.3 When crops are harvested and taken away the plant nutrients in them are taken away as well.
3.4. Fertilizing the soil increases the yield of the crop and so gives us more to eat or more profit.
4. There are 5 ways of fertilizing the soil:
4.1 Dig in well rotted compost.
4.2 Dig in a green manure such as coupe when the flowers have formed.
4.3 Dig in grey white plant ashes.
4.4 Pour liquid manure around the plants.
4.5 Use chemical fertilizers made in factories.

Resource material
1. To fertilize means to make the soil richer by adding plant nutrients which will make the crops grow better and produce a greater yield when they are harvested.
2. There are 4 reasons why you must fertilize the soil:
1. Some soils have been formed from rocks which did not have enough of the chemicals which make plant nutrients. In some tropical countries the parent rock had little potash in it and so the soil formed from that rock will be deficient in potassium.
2. Soils may lose plant nutrients when rainwater washes through them. This is called leaching. Soils which have an open texture and do not have enough clay and rotten plant material in them lose a lot of plant nutrients by leaching.
3. When a crop is harvested and taken away some plant nutrients are taken away as well. You must replace these plant nutrients if the soil is to remain fertile and produce good crops. Some plants need more of a particular plant nutrient than others and they take away a lot of that plant nutrient when they are harvested.
4. Fertilizing increases the yield of a crop and allows us to feed more students or make more profit if you sell the crop. The work done in making compost and adding it to the soil is rewarded by an increase in the amount of food for the school kitchen. The cost of buying fertilizer is rewarded by an increase in profit.
3. The plants get only a small amount of their total plant nutrients from the soil, most of them come from the air, but crops will not grow well unless you fertilize the soil to give the plants all the plant nutrients they need.
4. The amounts of different plant nutrients in a typical plant:

Plant nutrients from the soil	7%
Hydrogen from soil water	7%
Carbon from carbon dioxide gas in the air	42%
Oxygen from air and soil water	44%

6.9.15.1 Plant nutrients
Divide the plant nutrients into the following types:
1. Primary plant nutrients
One or more of these usually limits the yield of a crop, i.e. if there were more of this plant nutrient in the soil the yield would be greater. These are the most important plant nutrients. They make from 2-6% of the dry weight of plants.
nitrogen N,
phosphorus P,
potassium K. (potash is potassium oxide)
2. Secondary plant nutrients:
They are needed in smaller amounts than the primary plant nutrients to make the plant body for normal growth. There is usually enough of these in the soil for good crop yields.
sulfur S
iron Fe
calcium Ca
magnesium Mg
3. Micronutrients (sometimes called trace elements)
Plants need the following chemical elements in very tiny amounts for their normal growth:
boron B
chlorine Cl
cobalt Co
copper Cu
manganese Mn
molybdenum Mo
zinc Zn
4. If a soil does not have enough of a particular plant nutrient, e.g. nitrogen, you say that the soil is deficient in nitrogen. The only sure way to find out whether a soil is deficient in any plant nutrients is to ask a field officer of the Department of Agriculture to send some of the soil to a laboratory for chemical testing. However, you can tell if the soil is deficient in plant nutrients by examining your crop plants carefully. If a plant does not look healthy because there is not enough plant nutrient you say that it shows deficiency symptoms.

If the plant has not enough of this plant nutrient:	The plant shows these deficiency symptoms:
Nitrogen, N	The plants are small and they have few leaves which are pale green or yellow. The lower leaves look burnt and die early
Phosphorus, P	The plants are small and do not grow strongly. The leaves are a blue green colour and are usually purple underneath. The lower leaves die early. They take a long time to produce fruit which are small and badly shaped.
Potassium (potash), K (K₂O)	The plants have small main shoots but many side shoots. The leaves have dead white areas on the leaf edges and later die.
Sulfur, S	The plants are small with pale green upper leaves.
Calcium, Ca	The plants are small with unusually shaped leaves. The shoot tips may die.
Magnesium, Mg	The leaves have green veins but are pale yellow in between.
Iron, Fe	The younger leaves look yellow. The lack of a healthy green colour in the leaves is called chlorosis and this may be due to a deficiency in one or more plant nutrients.

6.9.15.2 Green manure
Many legumes such as cowpea and lablab bean are grown until the flowering stage and then dug into the soil. When this plant material rots it leaves nitrogen and other plant nutrients in the soil both from the leaves and root nodules. The root nodules contain bacteria called Rhizobium which take in nitrogen gas from the air and change it into organic compounds. However, it is unlikely that green manure crops alone can keep the soil fertile. You will probably have to use other fertilizers. The best green manure crops have lots of soft green leaves and grow upright so it is easy to dig them into the soil before the seeds form. The day before digging in a green manure crop wet the soil if it is dry. After digging in, keep the soil damp but not wet. Dig the bed over again after 3 weeks and it should be ready for sowing with a new crop in another 3 weeks.

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.
If you want to teach more lessons on legumes see the Resource Material at the end of the lesson.
Method
Divide the class into groups of 4-5 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: 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 bacteria called Rhizobium 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 (Leguminosae). Most of the plants have lumps on their roots called nodules. Bacteria called Rhizobium 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.
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.

6.9.16.1 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 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. Erythrina.

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 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
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
Prepare a slurry by mixing the contents of the packet with 500 mL water for small packets and 2,000 mL water for larger packets.

Useful legumes
6.9.16.8 Mung bean (Phaseolus aureus)
See diagram 5.0 Mung bean
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 - 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 3-4 days. Before cooking Mung bean the seeds should be soaked in warm water overnight and that water thrown away.

6.9.16.9 Cowpea (Vigna unguiculata) Cowpea come from Africa and many varieties have been produced, e.g., snake bean or yard long bean or asparagus bean and sitoa 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 (Phaseolus vulgaris) or 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. 38 This is 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 (Psophocarpus tetrogonolobus) or "as bin" or Goa bean.
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 x 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 break down 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
See also 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).
Preparation
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 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. 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. Now 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) - (returns from Blocks 2 and 3) - cost of fertilizer used.
Cost of fertilizer in bags = (cost of fertilizer + freight) X (weight of fertilizer used / weight of whole bag of fertilizer)
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. If you want to teach more lessons on fertilizers see the Resource Material at the end of this lesson.
Method
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.

Resource material - Fertilizers
6.9.17.1 The 2 types of fertilizer
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	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:
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.
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.
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.
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.

6.9.17.2 Common fertilizers, "straight fertilizers" or "simple fertilizers", contain N nitrogen, P phosphorus, K potassium, and S sulfur.

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	-	-
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

6.9.17.3 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.

6.9.17.4 Plant nutrients
Plant nutrients may be found in the rock that the soil is made from, or in the soil particles, or held loosely in the soil usually attached to the very small clay particles. Plant nutrients that are loosely held like this can easily be used by plants. The roots of the plants can take these nutrients from the soil. These plant nutrients are available to the plants. However, sometimes plant nutrients are in the soil but the plants cannot use them they may not be available to the plants. Quite often this happens because the soil is too acid or too alkaline. Most plant nutrients are available to plants when the soil is slightly acid. If the soil is too acid, you can add some lime to make it more alkaline. Dark swampy soils are often too. acid, so you can make them less acid if you put drains in the soil and make it less wet. Soils made from coral rocks or coral sand or limestone are often too alkaline. You can make these soils less alkaline by mixing the soil with some acid, or by mixing some rotten compost with the soil or by adding ammonium sulfate fertilizer with the soil.

6.9.17.5 Acidity and alkalinity
The acidity of a soil is measured by what is called 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)

6.9.17.6 Soil acidity
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, then 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

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, e.g. "Trade Name", Carbaryl Insecticide 75 g net. Tell them what this means: "XXXX" is the name of the company which makes the insecticide "YYYY" is the trade name of the chemical "Carbaryl" is the common chemical name, "75 g net" is 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 "YYYY" 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 - 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:
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 made-up 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 - 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 for 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 - 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 s 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 (grammes 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: Slightly toxic, 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 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 Types of insecticides
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.
3. Common pesticides
For a list of common pesticides, See Appendix K

6.9.19.0 Sprayers and dusters
Preparation
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 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 - 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.
(g) Do not spray in the wind or rain.
(h) When spraying walk evenly at about one pace each second. Give each plant an even covering.
(I) 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 - 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 kinds of information you will need are:
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. You should be able to discover new information to allow you to add to Appendix M.
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 - Production Costs - 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.

Method
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:
1. Returns $.
2. Production costs
3. Seeds $
4. Fertilizer
5. Establishment costs
6. Nursery
(g) Miscellaneous, plastic bags etc.
4. The students can now calculate the profit of this project.
Establishment costs 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.