Short-Term Benefits of Grain Legume Fallow Systems on Soil Fertility and Farmers Livelihood in the Humid Forest Zone of Cameroon

Soil fertility management of smallholder farms in the humid tropics is a major issue as a result of inherently low fertility with nitrogen being the most limiting plant nutrient. Use of grain legume fallows could improve soil quality through nitrogen fixation and ensure food and nutritional security in developing countries. This field trial was laid out in a Randomized Complete Block Design (RCBD) to evaluate the short-term benefits of grain legume fallows (common bean, groundnut, cowpea, and soybean) on soil fertility improvement and income generation in relation to a natural weed fallow system. The results showed that total soil nitrogen content ranged from 0.19–0.24%, and differed (P < 0.001) significantly with the highest in common bean plots as compared to the others. The soil organic carbon (SOC) content was highest in cowpea plots (3.36 %) and lowest in the natural weed fallow (2.77 %). However, the SOC were not significantly different among the fallow systems but were higher than the SOC of the soil before sowing (2.41 %). Grain yield ranged from 1.0–1.9 t/ha and differed (P < 0.001) significantly. The highest profitability of integrating grain legumes in farming systems was recorded in the groundnut fallow, followed by soybean, and bean. Cowpea generated a negative return, while the natural fallow system had no effect. Integrating grain legumes fallow into agricultural systems in the humid tropics enhance the value of the fallow lands and may serve as viable short-term economic incentives for smallholder farmers.