B5.1 The Importance of Soil


An average soil sample is 45 % minerals, 25 % water, 25 % air and 5 % organic matter.

Source: European Commission 2007 



Soil covers most of the land surface of the earth. It is formed from rocks and decaying plants and animals. The texture of soil is determined by the different sized particles it contains, such as sand, silt and clay. It contains varying amounts of organic matter, which result from the decomposition of living organisms.

The organic matter is contained within the top layer, known as ‘topsoil’. It can take natural processes over 500 years to form 2cm of topsoil. This layer is the most productive layer.

Fungi and bacteria help break down organic matter in the soil, whilst earthworms digest organic matter, recycle nutrients and make the surface soil richer. Roots from plants loosen the soil, which allows oxygen to penetrate it, benefiting any animals living in the soil. Roots are also extremely important as they hold the soil together and help prevent erosion.

Soil provides important functions. Aside from allowing us to grow crops, it helps to clean water and reduce flooding. Good quality soil (soil that is working as it should) filters out potential pollutants and therefore protects underground water supplies. Soil can also store 3,750 tonnes of water per hectare.

We use soil to grow crops, which feed us and feed our animals. To be productive, the soil must be managed properly. If the soil loses organic matter or the structure of the soil degrades, soil erosion may occur. This may then affect the nutrient and water storage levels, which will affect crops.

If soil is in poor condition and cannot retain water, water-run off will occur. This may cause pollution of water as pollutants are washed into watercourses. Soil itself is a pollutant in this manner.

Some types of soil are a raw material, for example, the construction industry may use soil as a foundation for building. In addition, some types of soil are valuable as a resource, such as peat.

We must consider soil to be a non-renewable source. This is due to the length of time it takes natural processes to form it.