THE SOIL

Soil is important to plants because it supports plants and provides them with water and food.

KINDS OF SOIL

Soil can be divided into three kinds depending on its structure

1. Sandy soil: contains more sand and therefore drains water very quickly and becomes dry.
2. Clay soil: contains very tiny particles and therefore has poor drainage and aeration.
3. Loam Soil: is a balanced mixture of sandy soil, clay soil and humus. It has good drainage, aeration and contains water and mineral salts.

 

Therefore, loam soil is the best soil for farming-

1. WHAT SOIL IS MADE OF SOIL CONTAINS SOLID PARTICLES

 

ACTIVITIES 12a

Humus Take some soil in a long glass jar and fill the three quarters of it with water. Shake well and place the jar on a table. The bigger stones go down faster. The tiny particles take a very long time to settle. Different solid particles are found in different layers.

 

2. SOIL CONTAINS VIUMUS Humus is the part of soil which is formed by rotting leaves, Grass and animal remains. Advantages of humus in soil: Humus provides valuable mineral salts to plants, retains water in the soil and absorbs heat from the sun. See the humus Moating on water in the above diagram

SOIL CONTAINS WATER: Plants need water to make their food and for transpiration

3. Take a lump of soil from your garden and weigh it. Spread it on a paper to dry, there any difference in its weight? The difference gives us the Weigh it again amount of water in the soil
4. SOIL CONTAINS AIR: Air in the soil is required for the plants as well as the animals in the soil for respiration.

Drop a lump of soil into the water in a jar and watch. Why are the bubbles coming out what does this experiment prove?

3. SOIL CONTAINS LIVING THINGS: They include insects, earthworms, rats, rabbits, snakes and snails. They make burrows in the soil so that water and air can get into the soil easily. The earth worm is called ‘nature’s plough’ or ‘farmer’s friend’ a they bring the underground soil to the surface and make them fertile by their dropping. Unlike other animals, each earthworm contains male and female reproductive organs.

Soil also contains minute living things called Bacteria which produces salts for the plants.

III WHAT MAKES A SOIL FERTILE?

A proper mixture of gravel, sand, clay, humus, water, air and living things in the 50 make it good for plants to grow in. The humus forms the food of the plants. A Soil which has sufficient plant food in it is called a fertile soil. After every crop, the so becomes less fertile. We have to make it fertile by adding more plant food.

HOW TO MAKE SOIL MORE FERTILE

1. BY ADDING NATURAL MANURES: They include:-
2. a) Farmyard manure, like cow dung, poultry manure and pig manure.

form humus

1. b) Green manure: like leguminous plants specially grown and buried in the soil.
2. c) Compost and sewage disposals.
3. d) Woodash; which is a chief source of potash. But charcoal will not enrich soil as it does not dissolve in water, Natural manure remains in soil for a long time and they do not cost much to the farmer.

BY ADDING ARTIFICIAL FERTILIZERS: These are different kinds of chemical compounds or salts which contain nitrogen (N), Phosphorous (P), and Potassium

(K). Ammonium nitrate, super phosphate, potassium sulphate, D compound etc are all artificial fertilizers. Nitrogen chemicals in Kafue produces fertilizers in Zambia.

CAUTION: Fertilizers should be applied very carefully so that they do not touch the plants or their leaves. If they do, it may damage the plants.

BY ADDING LIME TO ACID SOIL

1. a) Lime neutralizes or corrects acid soil.
2. b) It improves the structure of clay soil.
3. c) It provides calcium one of the nutrients to plants.

BY FOLLOWING A RIGHT CROP ROTATION:

Growing different crops one after another each year so as to rotate them on the same land in an order is called crop rotation. A common rotation for a vegetable garden is shown below.

Advantages of Crop Rotation:

1. a) It helps to keep the supply of humus and other nutrients in the soil.
2. b) It reduces plant diseases, pests and weeds.
3. c) It reduces soil erosion.

LEGUMES

 

5. BY MULCHING PLANTS: Placing cut grass or leaves thickly around the stem of growing plant is called mulching. It can be used on trees like bananas, citrus tree and pawpaw.

Advantages of Mulching:

1. a) It reduces evaporation from the soil and keeps moisture.
2. b) It enriches the soil by adding humus.
3. c) It reduces soil erosion.
4. BY PREVENTING SOIL EROSION

WHAT IS SOIL EROSION Soil erosion is the carrying away of the good top soil by rain or wind.

Causes of erosion:

1. a) Deforestation or destroying plants by cutting them down or by fire. Roots of plants hold the soil together and stop it from getting washed away.
2. b) Bad ploughing: loosens soil and destroys its structure.
3. c) Burning: makes the soil dry and dusty to be blown away by wind.
4. d) Over grazing or a complete removal of plant and grass by animals, dries out the soil quickly. It may be eventually blown away by wind or washed away.

How soil erosion can be prevented

1. a) Reafforestration: by planting trees in mountainous and sloppy areas.
2. b) Contour Ploughing: or ploughing at right angles to the slope so that the furrows will be able to trap water.
3. c) Controlled burning: Bush or grassland may be burned just before the rainy season starts
4. d) Mulching: over the soil will protect it from erosion.
5. e) Terracing or building terraces or steps across a slopping field.
6. IMPORTANCE OF TREES IN SOIL CONSERVATION
7. Water evaporates from trees and causes rain.
8. Leaves decay and add humus to the soil
9. Roots hold the soil together and reduce soil erosion.

Destruction of trees reduces rain and ruins the soil. It turns good lands into deserts.

*Sahara” was a fertile land once and it became a desert due to destruction of trees.

 

HOW TO MAKE COMPOST: Compost is a rich and cheap manure which can be prepared from garden refusals, dead plants, leaves and animal droppings.

Activities: (120) Make a pit of about 1 metre wide and s0 cm deep. Fill it with garden refusals and leaves to a depth of 15 cm. Spread soil and animal droppings to make a 5cm bags to protect it from the sun and rain. Sprinkle water on each layer, if the leaves are thick layer. Repeat this until it becomes a heap of about 50 cm high. Cover it with plastic paper wet. In about four months it will be changed into a rich manure.

BY MULCHING PLANTS: Placing cut grass or leaves thickly around the stem or growing plant is called mulching. It can be used on trees like bananas, citruses and pawpaw.

Advantages of Mulching:

1. a) It reduces evaporation from the soil and keeps moisture.
2. b) It enriches the soil by adding humus.
3. c) It reduces soil erosion.
4. BY PREVENTING SOIL EROSION

WHAT IS SOIL EROSION Soil erosion is the carrying away of the good top soil rain or wind.

Causes of erosion:

1. a) Deforestation or destroying plants by cutting them down or by fire. Roots of plants hold the soil together and stop it from getting washed away.
2. b) Bad ploughing: loosens soil and destroys its structure.
3. c) Burning: makes the soil dry and dusty to be blown away by wind.
4. d) Over grazing or a complete removal of plant and grass by animals, dries out the soil quickly. It may be eventually blown away by wind or washed away.

How soil erosion can be prevented

1. a) Re-afforestation: by planting trees in mountainous and sloppy areas.
2. b) Contour Ploughing: or ploughing at right angles to the slope so that the furrows will be able to trap water.
3. c) Controlled burning: Bush or grassland may be burned just before the rainy season starts.
4. d) Mulching: over the soil will protect it from erosion
5. e) Terracing or building terraces or steps across a slopping field.
6. IMPORTANCE OF TREES IN SOIL CONSERVATION
7. Water evaporates from trees and causes rain.
8. Leaves decay and add humus to the soil
9. Roots hold the soil together and reduce soil erosion.

Destruction of trees reduces rain and ruins the soil. It turns good lands into deserts

*Sahara” was a fertile land once and it became a desert due to destruction of trees.

HOW TO MAKE COMPOST: Compost is a rich and cheap manure which can be

prepared from garden refusals, dead plants, leaves and animal droppings.

Activities: (12d) Make a pit of about 1 metre wide and 50 cm deep. Fill it with garden

refusals and leaves to a depth of 15 cm. Spread soil and animal droppings to make a 5cm

thick layer. Repeat this until it becomes a heap of about 50 cm high Cover it with plastic

not wet. In about four months it will be changed into a rich manure.

bags to protect it from the sun and rain. Sprinkle water on each layer, if the leaves are

EXERCISE

Give reasons for the following.

1. Plants grow well in the soil which contains plenty of humus.
2. Well drained soil is required for crops.
3. Living things are important in the soil.
4. Earthworm are a friend of farmers.
5. Fertilizers should not be allowed to touch the leaves or stems of plants.
6. Lime is added to some soil.
7. After growing cabbage it is better to grow beans.
8. ‘Mulching’ is good for plants like lemons.
9. Grass and bushes should not be removed from uncultivated lands.

10 Farmers should be encouraged to use plenty of compost.

II a) What is a fertile soil?

1. b) How will you make a land more fertile?