Cover Image
close this bookBetter Farming Series 04 - The Soil: How the Soil is Made up (FAO - INADES, 1976, 37 p.)
close this folderDifferent kinds of land
View the document(introduction...)
View the documentThe soil
View the documentThe subsoil
View the documentThe parent rock
View the documentExamples of different soils


There are several kinds of land, for example:

cultivated land the fields that are farmed;
cultivable land fields that can be farmed only if they are cleared;
land that cannot be farmed, because nothing grows on it; you cannot farm stone or laterite.


In your village maybe a hole has been dug, in order to make a well, or to get earth to make bricks.
Or maybe a ditch has been dug between two fields.
Let us dig a hole ourselves.
Let us dig it deep, and quite straight.

What do we see?
The soil is made up of different kinds of earth, of different layers.

These layers

· are not of the same colour; that on top is often darker.

· are not of the same depth.

By making a hole you can see the layers of soil

· In the first layer we find roots; this is the soil.
The soil is the layer of earth where roots find their food.
The soil is more or less deep.
The soil is more or less rich in food.

· Below the soil is a harder layer.
It is difficult to make a hole in it.
This is the subsoil.

· Even deeper is rock, called the parent rock.

Sometimes you can very clearly see the difference between two layers.
Sometimes the layers are alike.
You cannot see the difference very clearly.

Good land: it has deep soil

The soil

Let's take a look at the hole we dug.
The earth where we find roots is the soil.
The soil has several parts.

· On the surface is the cultivated soil.

This first layer is what we work; we turn it over with a hoe or a plough; we pile it up in mounds or ridges.

In this layer you find living roots, for example, creeping roots (see Booklet No. 1) or fibrous roots (see Booklet No. 1). This is where they find their food. You also see dead roots and rotting leaves and stems.

The more this layer is deep and rich, the more fertile the soil is and the finer the plants are.

· Below this layer is the vegetable soil.

It is often lighter in colour and contains more sand.
Tap-roots go through this layer when it is not too deep (see Booklet No. 1, page 23).
There are often little pebbles below this layer.

The subsoil

The subsoil is often very deep.
It is always very poor.
It has little mineral salts (see Booklet No. 1 page 19).
It is hard and difficult to dig.
It is here that tree roots find their water during the dry season.

The parent rock

Below the soil and the subsoil we find stone or rock.
This rock is very hard.
It changes very slowly into earth.
This is the parent rock.


Fields are very different one from another.
The depth of the different layers varies a great deal.
Some layers may be missing altogether.

Examples of different soils

· Savanna soils

The depth of soil varies a great deal.
Often the soil is missing.
You can see the pebbles.

Bad savanna soil

The subsoil is very unstable.
It may become very hard.
Then a hardpan forms.
Roots cannot penetrate it.
Nothing can be grown on it.

· Mountain soils

In the mountains there is often neither soil nor subsoil.
You can see the parent rock and nothing grows.
If there is a little soil on the parent rock, a few small trees and some grass grow among the stones.

· Forest soils

The soil is rich.
The subsoil is always very poor; it contains no mineral salts; it does not become hard and does not form a hardpan.

· Soils of the same village

In various fields of the same village the layers of soil can be very different. On the slopes, for example, the soil may have been carried away by the rain.
That is why the soil is deeper in the valleys.

Soil is deeper in the valleys