Soil

Author: Garry Paterson - Soil Science Society of South Africa

( Article Type: Explanation )

Soil, along with sunlight and water, is essential for our life here on earth. All the plants that grow on the earth (including all of the crops that we eat and the grass that our animals eat) need soil to grow, and we even need soil to form the bricks to build our houses.
Soil is obviously not the same everywhere – it can be red, black, yellow-brown grey or virtually anything in between. Farmers and gardeners need to know what sort of soil they have in their area in order to know what sort of crops will grow best and, just as importantly, to realize what crops will not grow at all.
However, the most important thing about soil is that we need to keep it where it is! Simply put, soil is very fragile, and if the grass and other plants on the soil surface are removed, the roots that help to hold the soil together are no longer there, so the soil can easily be washed away by water or blown away by wind.
The dust that we see blowing into the air in winter is actually loose soil that is disappearing before your eyes. It has been estimated that South Africa loses around 300 million tons of topsoil per year, which will not return.##### Soil changes across the landscape, often suddenly, but usually gradually, and a change in any one of the properties listed above will have a significant effect on the uses to which the soil may be put, as well as how susceptible it is to disturbance (such as erosion, contamination or compaction). The soil properties that are most important to know about include texture (sand, silt and clay composition), structure (blockiness or crumbliness), leaching status (acidic or alkaline), degree of wetness (temporary or permanent) and effective depth (depth to which water and/or roots can penetrate).
It is thus vital that a trained soil scientist looks at all relevant soil aspects before any proposed development (whether mining, housing, commercial or power generation) so that the correct recommendations can be made and the proper measures taken to conserve the soil. This step is actually written into the environmental legislation in South Africa. The soil scientist will then produce a soil map of a particular area, which can then be interpreted for many different uses, is often a vital element in planning the wise and sustainable use of a piece of land.
South Africa has developed its own, relatively easy-to- use, soil classification system, so that we can accurately classify and map the soils occurring here. We are also one of the few countries in the world who have mapped the soils of the entire country at a 1:250 000 scale, and thus developed a digital database of the distribution and properties of these soils. This is a vital resource for a wide range of planning purposes, not least of which is the knowledge of where our best agricultural soils are located.
Remember, soil takes thousands of years to develop, but can disappear in less than a day (ask yourself: Why are most of the rivers in both our cities and rural areas brown?) If we don’t realize how fragile our soil resource is, and how quickly and easily it can become irreparably damaged, the future of our food and fibre production is under serious threat. If we look after the soil, it will help to look after us.