Natural soil

 Natural soils are influenced by rainfall and temperature,heavy rain causes the soil to become leached. High temperatures increase the rate of decomposition of organic matter in the soil, thereby lowering its humus content. Thus, climatic conditions tend to produce poor soils in the tropics and rich soils in the temperate regions. Besides climate and vegetation, the parent rock material also contributes to the quality of the soil. For example volcanic rocks tend to produce fertile soils.

   Laterite, a red soil which is a product of leaching, is commonly found in the tropics. It is composed mainly of iron and aluminium compounds,and poor in humus and essential plant nutrients, such as phosphorus, nitrogen and potassium. The black and brown soil of the temperate grasslands are the world's richest soils, with a high mineral and humus content. The light coloured desert soils tend to be very rich in minerals but have a low humus content.
   Mainly the soils are generally poor. Lateritic soils are widespread especially in the Guinea and Sudan savanna belts. The soils of the coastal regions are sandy or alluvial. These soils are also leached. The rain forest soils quickly lose their fertility under cultivation. In fact, the rain forest are a result of climatic conditions, not soil fertility. The brown soil of the north,Kano in Nigeria, are relatively rich and intensive agriculture is practised in these regions.