Soil is the uppermost layer of the earth that supports the growth of higher plants, mainly by providing a medium for plant roots and supplying elements that are essential to the entire plant.

The soil is the regulator of water supplies in rivers, lakes, and underground aquifers; it recycles raw materials such as hummus and is a habitat for soil organisms, including beneficial organisms, predators, prey, producers, consumers, and parasites.

Soil type, fertility, and the present and potential systems of soil management have considerable influence on agricultural production. Regional variations in soil types often influence the prospect of growing particular crops in different parts of the country. Also, fertility level influences soil types and traditional soil management techniques used in their maintenance.

The biological factors are complex and include the soil fauna and flora.

1. Soil Fauna

This includes both beneficial and damaging animal organisms. Beneficial organisms are those that break down and incorporate crop residues and further aid in water movement and aeration e.g. earthworms. The damaging organisms consist of the larval stages of click beetle/wireworms, crane fly, chafer grubs, and eelworms/nematodes.