AFRICA our HOME - SOIL by Tusk Trust

AFRICA

Our Home SOIL Revised Edition

SOIL

This chapter is all about soil, how it is formed, how it is lost, and how to look after it. Even the smallest child can play a part in looking after the crucial resource underneath our feet.

SOIL IS THE MOTHER OF ALMOST EVERY MOUTHFUL OF OUR FOOD.

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HOW THE SOIL IS MADE

If soil is the mother of our food, the sun is the father. Through a process called photosynthesis, plants harness the sun’s energy to make their leaves, flowers, fruits and woody stems, taking the raw materials they need from the soil. Herbivores (plant-eating animals) eat grass and other plants, converting them into muscle and skin and all the different parts of their bodies. Then carnivores (meat-eaters) eat the herbivores. This is known as a food chain. Nature recycles everything. Plants drop their leaves or die, animals leave their droppings or fall dead to the ground and rot, but nothing is lost.

Plants eaten by herbivore

Plants grow (photosynthesis)

Broken down by decomposers like: • Dung Beetles • Millipedes • Termites • Fungi and bacteria

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Herbivore eaten by predator

Animal decomposes

Body goes back to the soil

All the left-over organic matter is processed by the soil creatures and turned back into raw materials ready to be used again by the plants. The most direct way to get energy is to eat plants. At each step in a food chain, energy is lost as animals use up energy to grow, move and reproduce. Therefore, land can support many more human beings if people eat plants, rather than eating grazing animals. The number of people in the world is growing all the time, and some say that it would make sense for humans to eat more plants and less meat. Despite this, global meat consumption grows at 5% each year. Some people of course have no choice but to eat meat, or their culture is based on it. Around a billion people derive a livelihood from animals. More than three quarters of these are the world’s rural poor.

THE WONDER UNDERFOOT

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Soil is a fragile resource, created over decades. In parts of Sub-Saharan Africa, it takes around forty years to create one millimetre of topsoil. How is the soil made? Originally, much of the land we now use for agriculture was under forest. Soil is created from fallen leaves, wood, other plant parts and the breaking up of rock underneath. Soil animals move and feed in the organic matter, breaking it down and forming soil. Of course in order for soils to form, the temperature and climate has to be right for animals to live. Almost a third of Africa’s land area is desert made of mineral soils with scarcely any life inside.

EROSION ALERT

Ninety-nine per cent (99%) of our food comes from the soil. Yet soil is in danger! Each year, Southern Africa loses more than ten thousand million wheel-barrow loads of soil to erosion. Soil erosion is the process whereby soil gets worn away over time. When the trees, scrub and grassland are removed by people who wish to grow crops, graze animals or use the wood then the main source of organic matter and shelter is also taken away. Parched by the sun, washed by water, blown by wind, eventually, the soil is no longer fertile. Nothing can grow in it. 70 | Soil

In Southern Africa, 70% of people depend directly on the land for a living. Yet nearly half the region is unsuitable for cultivation as a result of poor soil quality and lack of water. Nearly 7 million square kilometres of land in sub-Saharan Africa are in danger of desertification. Soil erosion and degradation can even create famine and fuel war. In the Sahel, civil conflicts already occur as a result of desertification. Overgrazing causes half of all soil degradation. Unfair sharing of available land, overpopulation, and inappropriate farming methods all contribute.

The soil is like a human body. In order to flourish it must be fed and nurtured. If we force the soil to work for us, growing our food year after year, and give it nothing in return, eventually, it dies.

NURTURE THE SOIL AS YOU WOULD A HUMAN BEING

JUST AS THIS MAN WILL DIE IF HE IS NEGLECTED, SO WILL THE SOIL.

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LIKE THE OLD MAN, THE SOIL NEEDS FOOD, SHELTER AND WATER TO LIVE.

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FEEDING THE SOIL

Feed the soil lots of organic matter! In order to grow, plants need the essential elements carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulphur. Matter can neither be created nor destroyed. This important law of physics applies to the nutrients which come from the soil to feed the plants. They must come from somewhere. They will not magically reappear in the soil for the next crop. When the crop is harvested, and removed, the nutrients which the plant has absorbed during growth are taken away. They need to be replaced. You can feed the soil artificially. If you have money to buy them, you can use chemical fertilisers to add nutrients to the soil. They work quickly and improve harvests, sometimes hugely. Yet they can bring many problems. They do not improve the texture and water-retaining abilities of the soil. They do not help provide a home for all the creatures, like beetles and earthworms, which make the soil. The nutrients can leach out of the soil into the rivers and sea, causing eutrophication (See page 51). They cost money. Unlike compost and mulch, they do not help create new soil, so the soil is soon exhausted. Organic matter is a much better soil food.

Compost Compost is one perfect way to make the soil healthier. It improves the structure of the soil, making it stronger and less susceptible to erosion. The organic matter holds water in the soil, and of course breaks down to feed the plants with nutrients. One Ugandan school has started a composting project. This girl is collecting up left-over organic matter from her food preparation - leaves, carrot tops, egg shells, banana and other fruit skins. She feeds the compost heap with this waste matter.

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The boy pictured is turning the compost. This brings in air and allows the creatures living inside to breathe. The living organisms, including tiny fungi, bacteria, worms, beetles and flies, gradually turn the household waste into a very rich compost for adding to the soil. All you have to do is build a compost heap and feed it your rubbish. ACTION SHEETS - 31: Practical Composting

Leguminous trees – Plants that nourish the soil This tree is Gliricidia sepium. Originally from South America, it was brought to Africa to help feed the soil. It belongs to the family of plants called the legumes. We have many native legumes, Acacias and Faederbia are examples. Leguminous plants have bacteria living in their roots which fix nitrogen from the air, delivering it to the plant to use in growth. Gliricidia or other nitrogen-fixing trees can be grown as a cover crop on fallow land – land which is resting between crops – to enrich the soil with nitrogen. Cover crops also stop soil being whisked away by wind or washed away by water. The leaves of leguminous trees can also be cut and dug in to feed the soil, as a green manure. ACTION SHEETS - 36: Planting nitrogen fixing trees, 39: Green Manure/ Cover Crop for Biomass Transfer

SHELTERING THE SOIL

The soil never wants to be naked. Sheltering soil means keeping it covered and disturbing it as little as possible. Mulch occurs naturally in forests. It is made of decaying forest leaves, twigs and branches and in it lives a huge diversity of fungal, microbial and insect life. Natural mulch is like a “bank”, storing the nutrients contained in organic matter and slowly making these nutrients available to plants. Without mulch, the living soil is robbed of its natural nutrient stores, becoming leached and dry. In nature, most environments without natural mulch are deserts. This girl from South Africa is mimicking the forest, covering the soil using leaves or straw or other cut organic matter. You can even mulch using newspaper! Mulching not only feeds the soil, it shelters it from sun, wind and rain, slowing down soil erosion. ACTION SHEETS - 34: Mulching, 42: Saving Soil and Water on Sloping Land

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Contour Farming On sloping ground water runs off faster, gathering momentum to bring soil with it. In Zambia and Malawi, farmers ridge up the field with a hoe or with oxen-drawn ridgers. When the ridges run down the slope, the furrows in between act like drains. Tonnes of topsoil are washed off the ridges and carried away. Ploughing parallel to the mountainside prevents all of these problems. This picture shows farmers in Kenya working on terraces which break up the slope of a hill into levels which catch water and soil to prevent erosion.

LIVING FENCES FARMING CONSERVATION

Trees slow down and divert the wind. They provide leaves to feed and protect the soil. Pictured is a living fence from Burkina Faso. A living fence, made of plants combined with wire, provides the service of keeping people and animals off your fields, but they are also brilliant for many other reasons. They can provide: firewood, fodder, sustenance for people (such as fruit), wind breaks, fertiliser, mulch, erosion control, forage for small mammals, increase in crop yield, fibres for cloth, shade, construction materials, and medicines. If leguminous trees are planted, they can provide much-needed nitrogen into the system. Traditional living fences can be more durable than wooden posts, as they are less susceptible to termites and fungus. A women’s group in Moshi in Kikavu Chini, Tanzania, have taken a leading role in their community in educating friends, neighbours, and schoolchildren about wise farming practices. They distribute trees to every household in the village, to provide shade, windbreak protection and tree products for ongoing livelihood needs. Through educational trips to Olmotonyi Forestry Institute in Arusha, they learned about seedling propagation and tree nursery maintenance.

The boy pictured is chasing a goat away from his living fence, to help it to grow.

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Conservation Farming is a simple yet incredibly effective method of making the most of the available water, whilst conserving the soil. Conservation farming techniques are being developed for different climates and soil types throughout the world, and are making a huge difference to people’s lives. A key principle of conservation farming in Africa is ‘minimum tillage’ – disturb the soil as little as possible. Ploughing breaks up the soil surface. When it rains, the soil is washed away more easily. The Conservation Farming Unit in Zambia says: ‘Farmers who plough are at the mercy of a tradition that wastes inputs, time and ultimately destroys the soils upon which their future depends’. With no need to till the soil, no need for an ox and plough, there is less work to do, but harvests are better, because the soil is protected. Below is a boy from a project in Zambia making special pot holes. He puts compost in each hole, half covers the hole with soil and waits for the rains. The amount of compost you put into the dug holes is also critical - too much and you can ‘poison’ the crop. When the rain falls, he will plant seeds in the holes. Little ponds are formed in each hole, providing plenty of water for the crop. After harvest, the detritus from the crop is left on the soil, protecting the surface as a mulch.

ACTION SHEETS - 35: Agroforestry, 40: Living Fences, 41: Windbreaks

WATER IS SCARCE AND PRECIOUS

If too much water is pumped from the ground to feed the crops, and then the rains fail, the water stored in the ground will be used up and there may not be enough water for everybody to use. If people living up-river use more water for their crops, people living down the river may suffer shortages. You can read more about how people are working together to manage water in the Water chapter. This is a farm in Zimbabwe. The farmer is famous for finding ways to catch and keep the rainwater, so he can use it to nourish his flourishing crops. Behind his farm is a hill. He built rocky contour ridges to stop the water rolling away with the soil, with a reservoir at the bottom of the hill to collect the water and send it to an underground storage tank. In his cropland, he digs infiltration pits to catch the rain and let it slowly seep away into the soil. This helps fill the wells and ponds lower down the hill so he can pipe water to his crops in the dry season. Even the rain falling on his roof is harvested.

ACTION SHEETS - 42: Saving Soil and Water on Sloping Land, 43: Drip Irrigation, 44: Buried Clay Pot Irrigation, 45: Rainwater Harvesting for Crops

Watch the film on Harvesting water on the Farm

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MONOCULTURE

Farmers who grow one crop variety are farming a monoculture. The trouble comes when pests or diseases strike. Devastation rushes through the whole farm, as there are no crop varieties with resistance and no other crops to act as a barrier. Wild insects like ladybirds and spiders could have kept the pests under control, but they were made homeless or killed by pesticides. The whole harvest is lost.

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Working with Diversity On her farm in Ethiopia, this farmer grows many different crops and varieties. There is more chance that some crops will survive bad weather or an outbreak of disease. Mixed cropping also makes it harder for pests and diseases to spread. She uses less chemical pesticide, protecting the soil life needed for healthy fertile soil, and has chosen varieties that ripen at different times to spread the harvest over the year. If the price of one crop goes down, she will still make money from the other crops. After each harvest, she chooses seed from the best crops to save and sow next season. Over the centuries, farmers plant-breeding by seed selection has led to thousands of different crop varieties, each adapted to different climatic conditions and able to resist locally common diseases. These locally evolved varieties will grow well even if the farmer does not use chemical pesticides and fertilisers. ACTION SHEETS - 46: Setting up a Community Seed Bank

LOOK AFTER THE CREATURES WHO LOOK AFTER YOU

Soil creatures make soil. Bacteria, fly and beetle larvae live in the ground, eating through it and breaking it down into vital nutrients. Earthworms also munch through and produce very fine soil, perfect for plant growth. Dung beetle larvae actually eat dung, recycling it! Without them, we’d be up to our necks.

Some insects, bacteria and fungi attack the pests and diseases that destroy farm plants and animals. Ladybirds eat aphids and spiders will eat other pests.

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Birds too will help to destroy pest species such as grasshoppers. Pangolins, bats and monkeys can lend a hand if termites get out of control. Pesticides can damage these parts of agrobiodiversity. They are also poisonous and incredibly dangerous for humans if used without care!

Creepy Crawlies are crucial One third of every mouthful of food we eat comes from a plant which has been pollinated by an insect!! Destroying or damaging wild lands, the natural habitat of these useful animals and plants, will kill the wild creatures that help feed us. Of course, not all insects are friendly…

ACTION SHEETS 33: Natural Post and Disease Control

The world’s longest earthworms are found in South Africa, with a record length of 6.7 metres

WE CAN WORK TOGETHER

Eight ways to save our soil 1. Feed the soil lots of organic matter including compost and green manure. 2. Shelter the soil from wind and water with trees, cover crops and mulch. 3. Shelter the soil from over-grazing. 4. Shelter the soil from too much disturbance – till the soil as little as possible. 5. Find ways to save water and send just the right amount to your crops. 6. Grow lots of different crops to stop pests and diseases spreading quickly. 7. Look after the creatures who look after you – take care not to kill helpful insects. 8. Try out new ideas, and share information with others.

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Find out about permaculture – short for ‘PERManent agriCULTURE’. Permaculture farms and gardens are designed to use and recycle natural resources superefficiently, keeping soil healthy for the future. Many of the techniques described in this chapter are used in permaculture.

ACTION SHEETS - 78: Permaculture

SOIL

ACTIVITIES

ACTIVITY 1 Does it rot? or not? What does it mean if something is biodegradable? If something is biodegradable, then it will eventually decompose, or break down and become part of the earth. Try this experiment and find out which things are biodegradable and which things are not. Materials Large clay flower pot, small stone, soil to fill the pot, small assortment of waste materials (include something plastic like a piece of polythene plastic bag or a drinking straw, paper, vegetable peelings, leaves…) water, stick or rubber gloves, plastic bag, rubber band or string. Experiment Cover the hole in the bottom of the pot with a stone. Fill the pot 1⁄3 full with soil. Choose at least four different kinds of waste from your assortment and break or cut each into four pieces (BE CAREFUL to make sure you are not breaking anything that can cut you). Cover the waste with soil, filling the rest of the pot, and add water. The soil should be damp but not completely soaked.

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Cover the pot with a plastic bag and place a rubber band around it or tie it tightly with a string. Put the pot in a dark, warm place. Check the soil daily to make sure it is remaining damp. If the soil is dry, add water. After one month, empty the contents of the pot onto a newspaper. Spread the soil with a stick or with a gloved hand to see what has happened to the waste. What do you find? Which materials are biodegradable and which did not change at all? From: NatureWatch Magazine, UGANDA WILDLIFE CLUBS, March 1999

ACTIVITY 2 Investigate! Communicate! Contact an Agricultural Extension Officer to arrange a class visit to a farm using agroforestry techniques. Find out what trees the farmer grows on the farm, and ask all about their uses. What trees does he recommend planting? Make an exhibition about the visit and help spread good ideas! Strychnos cocculoides

Wild Orange

Sclerocarya birrea

Marula

Adansonia digitata

Baobab

ACTIVITY 3 A Model Farm Make two model farms and experiment to find out what farmers can do to save their soils!

Materials • 2 cardboard boxes (such as shoe boxes) • Plastic sheets (e.g. cut-up plastic bags) • Soil • Bricks • Sprinkling can or a tin can with holes punched in the bottom • Tape • Clear jars with wide openings • Water • Watch or timer • Materials for creating barriers, e.g. extra soil, stones, twigs • Paper and pencils for recording results Experiment Cut the 2 boxes down to size, cutting a V into one end of each. Line the boxes with plastic, and fill them with moist soil, packed down. Use bricks to set your two boxes on a slope with the V facing down. Place clear measuring jars right under the V’s. One of the boxes is a ‘control box’. It is a model of a slope where the farmer is doing nothing to reduce the flow of water over the soil. Do nothing to the soil in this box.

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The other box is for experiments. Do something to the soil in this box that you think will reduce the flow of water. You may build a barrier or dig a channel, or both. You can try having a barrier going up the hill, built at a random angle to the slope, or running across the hill. Record your experiment in a chart. Fill the sprinkling can with water. If you are using a tin can punched with holes, tape over the holes, and then fill the can with water, and remove the tape when you are ready to release the water. Hold the can of water about 30cm above the top end of the control box with soil, and remove the tape so the water sprinkles down onto the soil. Hold in this way until all the water has sprinkled onto the soil. Observe the water draining from the box into the measuring jar. Record how long it takes for water to drain into the measuring jar. Repeat the last step, but this time test the box containing your barrier. Record how long it takes for water to drain into the measuring jar. Once water has settled in the jars, measure and record the amount of water and the amount of soil that has drained into the two jars. Record this data on your chart. Repeat the experiment with different barriers/structures to see if you can reduce the runoff and soil erosion. Try changing the steepness of the hill. Record your results. Analyse your results and always ask why!

Record Chart Slowing the flow record What I did to the slope:

Remodelled the slope

Barrier Channel Other Materials used Direction of structure

up/down

across

random

Pattern of structure on slope (e.g. in line, diagonal pattern etc.) Time it takes for the water to drain into the collection jar Amouont of water collected Amount of sediment Based on Trees for Soils and People Activity Pack, Outreach/TVE