Introduction

The soil covering the surface of the earth has taken millions of years to form and we must conserve it. Soil is formed at a rate of only 1 cm every 100 to 400 years and it takes 3000 to 12000 years to build enough soil to form productive land. The most productive soil is the top layer, usually around 30 cm deep. Soil is a non-renewable resource and once eroded or destroyed it cannot be regained. If we disregard this, a time will come when there will not be enough soil left to sustain us.

Soil is the foundation of everything that we do, and need, to live. Soil is the growth medium for plants, a home for some insects, birds and animals, as well as a medium from which we get minerals, such as gold. Soil is used to grow our food, some of our fuels, fibres for clothing, timber for building and construction, and even the paper you are now holding in your hand.

We use products grown in the soil every day of our lives. It is important therefore to treat soil, especially topsoil, as a living entity and to conserve it for future generations.

The distribution of soils around the world is determined by climate and parent rock material, as well as the geomorphologic history of a given area. Lower-lying soils are more productive and fertile, whereas soils on steep slopes and at the top of hills are less fertile, but this also depends on the climate and parent material.

In some soils, especially tropical sandy soils, the productivity of the soil is inextricably linked with the plant community in it, for example tropical rain forests. The soil on its own is infertile, but the ongoing cycle of nutrients through decaying plants and animals ensures fertility.

The soil remains one of the most important natural resources on a farm and it is important to understand the texture and characteristics of the soil on the farm where you are working.