Crop rotation systems, in which maize is alternated with legumes, improve soil quality and reduce production losses.

Monoculture, or planting the same crop in a field season after season, leads to deprived soil and reduced yields. It’s our old friend common sense in the field again.

The weather, government policy and commodity prices are pretty much beyond the farmer’s control, but there is a lot he can do to reduce his risk. One obviously beneficial practice is that of crop rotation, says South African researcher, Dr Andre Nel of the Agricultural Research Council.

Cultivation systems that alternate maize with legume crops like cowpeas, groundnuts, soya beans and dry beans help to increase the profit and to keep input costs down.

“Crop rotation is the successive cultivation of different crops on a specific field to promote sustainability,” says Nel.

PROBLEMS WITH MONOCULTURE

Under a monoculture planting system the soil loses quality. This happens as root diseases increase because soil microbe activity weakens. Poor soils mean poor plant uptake of nutrients and water. In denuded soils weeds become a problem too.

Here’s the outcome – lower yields at harvest and bigger input costs for the next planting season.

ADVANTAGES OF ROTATION

Legumes in rotation with maize improve yields. They bind nitrogen in the soil, some of which stays behind after the legume crop has been harvested. The residual nitrogen is then available for the next maize crop.

A useful saving for the farmer who can reduce his fertiliser bill by putting in less nitrogen.

Crop rotation increases the variety and number of soil microbes. The importance of these populations under the soil surface is huge – without them the soil is simply a sterile growth medium.

Microbes suppress root diseases and encourage plants to put out large and efficient root systems.

When the alternative crop is introduced, the disease chain is broken because crop specific diseases cannot survive without their specific host.

Better disease control means less money spent on chemicals – another input reduction.

THE RIGHT CROPS

The best legumes to rotate with maize are cowpeas, groundnuts, soya beans and dry beans. Nel suggests that planting 25% to the alternative crop and 75% to maize is an option for farmers when they are committed to maize planting. This way at least 25% of the land is rotated.

Although it may seem a tough course to follow in the beginning, there is no doubt that rotating crops is part of good farm management.