Improving Soil Fertility and Crops Yield through Maize-Legumes (Common bean and Dolichos lablab) Intercropping Systems

Declining crops yield in the smallholder farmers cropping systems of sub-Saharan African (SSA) present the need to develop more sustainable production systems. Depletion of essential plant nutrients from the soils have been cited as the main contributing factors due to continues cultivation of cereal crops without application of organic/ inorganic fertilizers. Of all the plant nutrients, reports showed that nitrogen is among the most limiting plant nutrient as it plays crucial roles in the plant growth and physiological processes. The most efficient way of adding nitrogen to the soils is through inorganic amendments. However, this is an expensive method and creates bottleneck to smallholder farmers in most countries of sub-Saharan Africa. Legumes are potential sources of plant nutrients that complement/supplement inorganic fertilizers for cereal crops because of their ability to fix biological nitrogen (N) when included to the cropping systems. By fixing atmospheric N2, legumes offer the most effective way of increasing the productivity of poor soils either in monoculture, intercropping, crop rotations, or mixed cropping systems. This review paper discuses the role of cereal legume intercropping systems on soil fertility improvement, its impact on weeds, pests, diseases and water use efficiency, the biological nitrogen fixation, the amounts of N transferred to associated cereal crops, nutrients uptake and partition, legume biomass decomposition and mineralization, grain yields, land equivalent ratio and economic benefits.