Potential use of forage-legume intercropping technologies to adapt to climate-change impacts on mixed crop-livestock systems in Africa: a review

This paper summarizes effects of forage-legume intercropping on grain and fodder yield, land equivalent ratio, residual soil fertility, disease and insect pest reduction in mixed crop-livestock systems in Africa. In particular, it discusses the potential benefit of forage-legume intercropping in improving productivity, resource use efficiency and resilience of the system under climate change. Research undertaken in Africa demonstrates that intercropping forage legumes with cereals improves land intensification due to improvement in overall yield and soil fertility, and reduced risk of crop failure owing to rainfall variability, diseases, weeds and pests. Forage from intercropped legumes improves the intake of dietary nitrogen, digestibility of poor-quality feed, animal performance and efficiency of roughage feed utilization by ruminants. The improvement in digestibility alone leads to 15–30% reduction in methane emission per unit of animal product. Additional role that legumes may play includes lowering erosion (20–30%), reducing nitrogen leaching and carbon losses, and promoting carbon sequestration. Nitrogen fixed by legumes was on average 45 kg N/ha, and this ranges between 4 and 217 kg N/ha for herbaceous legumes and 8 and 643 kg N/ha for fodder tree species. Despite the many benefits of forage-legume intercropping, the current adoption rate in sub-Saharan Africa is very low. Future research aimed at selection of compatible varieties, appropriate plant geometry and temporal arrangement of the various intercrops under different locations and management scenarios, and minimizing the confounding effects of water, soil, light, microclimate and seeds could enhance adoption of the technology in Africa.