Crop Rotation

From an agricultural point of view, it is unwise to grow the same kind of crop in  the same farm year after year. When a farm is cropped continuously, its nutrients become completely used up. This situation is similar to an individual who withdraws money continuously from his savings account without  putting some money back into the savings. Eventually, his account will become exhausted and empty. A system of crop changing (rotation) is therefore necessary and must be planned in  such a way as to ensure that the nutrients are not completely used up. The planting of crop must follow a definite scientific sequence because different crops require different amounts of food. Some crops use many nutrients and are referred to as "heavy feeders " e.g millet and vegetables. Some plants can actually add nutrients to the soil e.g legumes. Crop rotation can therefore  be defined  as the planting of different crops on the farm as successive years in a scientific sequence without seriously reducing the soil nutrients.

Principles of crop rotation

(I) In planning crop rotation, deep  rooted plants e.g, ground should be followed by shallow  rooted ones, e.g . maize. This enables all the nutrients in every part of the soil to be used. A deep rooted plant draws its nutrients from deep down the soil profile, whereas shallow rooted plants derive their nutrients from the surface of the soil.

(ii) the growth of certain crops is favoured by certain nutrients. For example , repeated growth of maize uses up most of the nitrogen, whilst cassava uses up most of the potash.

Example of crops rotation plants are as follows:

Crops to plant

(a) Yams, cassava, potatoes (tubers).

(b) Maize , sorghum (grains crops)

(c) Mucuna, groundnut, cowpea (legumes).

Order to follow

(a) Grain crop should be planted after root crops.

(b) Legumes should be planted before tubers like yams, cassava and maize.

(c) crops which are attacked by the same pest and diseases should not follow each other.

(iii) All crops have their range of weeds , pests, and diseases. Certain weeds, pest and diseases also thrive very well with certain crops. If some crops are planted repeatedly , such diseases, pest and weeds will become a common feature in that area and will contribute to serious yielded losses. For example if yams are planted repeatedly in an area , the population of yam nematodes builds up, but if yam is alternated with maize, tobacco or cotton which are not affected by the yam nematodes, their population will be controlled.

(iv) The use of leguminous plants e.g. cowpea, mucuna and groundnuts is desirable in crop rotation. Leguminous plants are Important sources of soil organic matter, and they also have the ability to make nitrogen in their root nodules which are released later to enrich soil.

   Crop rotation is advantageous to the farmer in that it provides a variety of food items throughout the year. Crop rotation helps the farmer to control pest and diseases and increase soil fertility. In situations where land is not abundant, crop rotation provides a solution to such problems.