It has already been stated that environmental factors influence the type of crop which can be grown in any given area. Vegetation types merge into one another, owing to the gradual changes in climatic conditions in the various zones or regions such as West Africa.
The kind of agricultural activity that takes place in a given region will be affected by a number of ecological and social factors, but of these factors, especially over large areas, climate is by far the most important.
Each crop has a set of climate and soil conditions under which it will grow and produce good yield.
In Nigeria, different areas have different soil and climatic conditions. This has affected the distribution of crops.
In the southern humid areas of Nigeria, the most common crops are roots, tubers and tree crops. In the savannah and dry areas of the North, the common crops found are cereals and legumes.
Due to technical information which is now available on the requirements of various crops, a choice can be made of crops which are particularly suitable for growing under a range of known conditions. The use of techniques such as irrigation, however, make it possible to extend the normal range of cultivation of some crops, particularly annual ones. New varieties, which are tolerant to a wide range of conditions,also help to extend the range of cultivation of many crops.
Factors that affect Crop Distribution
Whether a crop is annual or perennial, there are several factors that determine where it is found.
Temperature and Humidity
Temperature may be expressed in a number of ways, e.g. mean temperatures of the day, week, month, or year. Or expressed as maximum and minimum for each of these periods. Different crops require varying ranges of temperature to grow well.
Wheat grows well under cool temperatures. It is grown in the northern states of Nigeria during the harmattan season but not during the rainy season when it is fairly warm. Potatoes also like cool temperatures and are therefore mostly grown around the Jos and Zaria areas.
Sunshine
All crops require sunshine to carry out photosynthesis and growth. Some crops require sunshine towards the end of their life cycle in order to give good yields. Cotton requires a rain-free period with adequate sunshine for the bolls to dry.
Rainfall
All crops require water in the form of rainfall or irrigation. Crops differ in the amount of water they require. Millet which requires little water is grown in the North of Nigeria. Maize which requires more water is grown mainly in the more southerly areas.
Activities of man
Man can affect crop distribution by modifying some of the natural factors. Examples are establishment of irrigation schemes in areas where the rainfall is not adequate, and the addition of fertilizers to soils of low fertility.
Soil conditions
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Soil types and soil properties vary from one place to another, sometimes within very short distances. Various crops require various soil conditions for good growth. Crops like millet and cassava can grow on poor soils of low fertility. Maize requires good fertile soils.
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