Examples of farming methods are:
1. Shifting cultivation: This is the practice whereby a farmer and his farming family move from one piece of land to another year after year, in search of virgin forest to clear and cultivate their crops. The hope is that uncultivated land will produce more yield of the crop than the cultivated land of the previous year. This practice results in extensive destruction of forest without making maximum use of the soils. This deforestation upsets the ecological balance and affects the vegetation of the habitat. Habitats of forest organisms are continually destroyed This method of farming was practised when farming communities were not heavily populated and had enough forests at their disposal. With increase in population and the use of fertilisers, this method has given way, in modern times, to other farming methods.
2. Bush fallow: In this method, a piece of land is cultivated until decline in crops yield is noticed. The land is then abandoned and left fallow to recover over a period of 8 to 10 years before the farmer returns to farm on the land again. Decline in crop yield indicates exhaustion of soil nutrients. The fallow period allows the piece of land to grow into a bush and most of its soil nutrients are replaced. This is a slight improvement on the shifting cultivation method. This method is widely practised in West Africa. The introduction of fertiliser has rendered fallowing unnecessary since deficient soil nutrients can be replaced by the appropriate fertiliser combination. This method affects the ecosystem the same way as shifting cultivation did.
3. Crop rotation: The crop rotation method is a kind of soil fallow method. In this method, a piece of land is cultivated continuously, but different types of crops, which use different layers (strata) of the soil are planted every season. For example, a surface feeder (uses nutrients from surface soil e.g. maize) is planted the previous year. This leaves the deeper strata of the soil fallow for the season the maize is growing. It is important to note that most monocot crops (sorghum, maize, millet, etc.) have a fibrous root and do not penetrate deep into the soil. They are referred to as surface feeders. Dicot crops on the other hand (yam, cassava, potato, etc.) have roots that penetrate deep into the soil and obtain nutrients at that level and are deep feeders. In crop rotation, therefore, crops with demand on different strata of the soil follow one another. Legumes normally have the ability to cause the fixation of atmospheric, nitrogen, restoring nitrogen to the soil, a process called nitrification. This makes it imperative to include legumes in a crop rotation regime to restore soil nitrogen. This nitrogen fixing ability of legumes comes from the presence of nitrogen fixing bacteria in the nodules of their roots. To maintain or boost soil fertility, it is necessary to add fertiliser and manure to the soil each season.
4. Monoculture: In this method, only one type of crop is grown. This requires extensive use of land to maximise production. It is wasteful in soil use because one crop is likely to make use of only one stratum of the soil. Another disadvantage of this method is multiplication of pests of the mono crop, because of the abundance of food made available to them.
5. Mixed cropping: This method improves on soil utility by planting two or more types of crops on the same piece of land e.g. planting a surface feeder (e.g. maize) and cassava (a deep feeder). Other forms of mixed cropping to maximise economic gains are planting cocoa, plantain and bananas together with yarns and sugar cane, etc. Because of the variety of crops, mixed cropping has the advantage of not allowing easy spread and survival of any crop pest.