A farmer may grow a few kinds of crops on a small farm and rear a few animals just to supply his family's needs. There is no surplus farm products for sale. This is known as subsistence farming. In commercial farming, a farmer cultivates the land and raises livestock for sale.
Shifting cultivation
This is a traditional form of agriculture which is practiced in the tropics and subtropics by societies which do not have permanent homes, but move from place to place. A farmer simply clears an area of bush by slashing the vegetation and burning it - commonly known as the slash and burn cultivation. He grows more than one type of crop on the clearing until the soil nutrients are used up, usually in about two to four years time. Then he abandons the land with no intention of returning to it, and moves on to clear and clear and cultivate another area of bush.
The used land lies fallow and is quickly invaded by plants and returns to bush. Litter from the Bush helps the soil to regain its fertility in about five to ten years.
Shifting cultivation is practiced by subsistence farmers and is associated with plenty of land and a sparse population. It is not an economical or practical method of farming today where producing food for an ever increasing population is one of our main problems.
Land rotation
Also known as bush fallow, this is a modified form of shifting cultivation. A farmer clears an area of bush; cultivates the land until it's fertility decreases; allows it to lie fallow to regain IRS fertility; and then returns to cultivate it again.
Like shifting cultivation, land rotation is an uneconomical and wasteful farming practice. It cannot provide for the needs of a rapidly growing human population. Often, the land is not left to lie fallow long enough to allow it to regain its fertility before it is cultivated again. This eventually damages the soil and converts the land into a barren desert. This form if farming is a major factor in the destruction of tropical forests. Many types of plants and animals that can only live in the conditions present in a typical forest also face extinction.
Pastoral farming
This is a traditional type of farming. Certain tribes keep only grazing livestock such as cattle, sheep and goats. They move with their livestock along the same routes at definite seasons of the year. These routes follow the rains so that the livestock get good grazing land. The routes also void areas infested with pest like tsetse flies.
The Fulanis in west Africa and the Masai in East Africa are well known examples of pastoral farmers. They provide for their families by selling meat, milk and hides.
In this type of farming , overgrazing of poor pastures may lay the land bare and expose it to soil erosion.
Crop rotation
In most countries, crop rotation has replaced land rotation and shifting cultivation. Crops in a rotation plan are grown on a piece of land in a particular order and rotated through a three, four, five or six year period. A well chosen crop rotation plan will allow the continuous use of land while maintaining soil fertility and controlling pests and diseases at the same time. This farming practices is, therefore , important in the present world where agriculturally suitable land is scarce and the population is large and increasing all the time.
Below explain a four year crop rotation plan suitable for west African soils. It includes shallow rooted crops (maize and yam) and deep rooted crops (cassava) so that these crops can use nutrients at different soil levels. It also includes a legume (cowpea) which will help to replenish the nitrate content of the soil.
