Strategies for improving nodulation and nitrogen fixation of leguminous crops to enhance production in smallholder farming systems

Leguminous crops have a special role of fixing atmospheric nitrogen in the soil through the process of biological nitrogen fixation. Biological nitrogen fixation is a natural means of reducing atmospheric nitrogen (N2) to ammonia in the presence of nitrogenase in a form available to plants. Low crop productivity is a problem facing farmers in Sub-Saharan Africa. These low yields in leguminous crops are as a result of declining soil fertility, reduced N2-fixation, soil acidity, over cultivation, poor soil management practices and this make soils deficient in Nitrogen, and Phosphorus making the soil susceptible to erosion and leading to land degradation. It has been reported that application of organic matter increased soil pH from 5.0 to 6.5 after 90days of application. Majority of farmers in Sub-Saharan Africa are unable to afford the high prices of mineral fertilizer and much of the fertilizers are imported and putting pressure on foreign exchange. Hence farmers are advised to intercrop with legumes or practiced crop rotation to help increase the nitrogen content of the soil as a way of increasing yield. This review paper tends to reveal ways of improving nodulation and nitrogen fixation by legumes to enhance production in smallholder farming systems.