Replenishing Marginal Soils Through Use of Agroforestry Systems in Southern Africa: A Case Study of Pigeonpea (Cajanus cajan L. Millsp) Improved Fallows in South Africa

Soil fertility degradation is occurring in almost all terrestrial biomes and agroecologies in southern African (SA) countries. However, its impact is especially severe on the livelihoods of the poor, who are heavily dependent on farming, and this has further pushed the farmers to cultivate on marginal lands. All three (biological, chemical and physical) forms of land degradation are being experienced on farmers’ fields. Some of the causes of soil fertility degradation are overgrazing, deforestation, climate change and unsustainable farming practices. Most studies conducted in SA showed that agroforestry systems (AFS) can replenish degraded lands through improvement of soil fauna, soil organic matter, nitrogen and carbon content, aggregate stability, infiltration and lowering bulk density and runoff. Pigeonpea improved fallows have been shown to double maize yields compared to traditional farming system (continuous maize without fertiliser). Agroforestry systems could enhance the resilience of agricultural production to current climate variability. It can be a long-term solution to this variability through utilisation of legume trees for intensification and diversification as well as buffering of farming systems. For scaling AFS in SA, there is need for policy interventions in each country. This will help in solving the challenges of soil fertility degradation and lessen the burden of buying expensive chemical fertilisers by vulnerable smallholder farmers.