Soil organic carbon (SOC) management for sustainable productivity of cropping and agro-forestry systems in Eastern and Southern Africa

Abstract

In Eastern and Southern Africa, the shifting from the no-external input agriculture (shifting cultivation through slash and burn) to intensified agricultural systems has resulted in widespread agro-ecosystems with high soil organic carbon and nutrient depletion. This is quite evident in farming systems with reduced fallow period or those that practice continuous cropping without or with little inputs. Long-term experiments indicate that losses of up to 0.69 t carbon ha⁻¹ yr⁻¹ in the soil surface layers are common. Such losses are commonly reported by farmers engaged in participatory community-based research development projects. This calls for judicious strategies for recapitalization or replacement of these depletions. Such strategies include direct SOC replenishment through addition of organic materials, notably manures, wastes, residues and plant litter; biomass transfer; incorporation of improved fallows in the farming systems. Indirect contribution to SOM replenishment or recapitalization may be achieved through inorganic fertilizations and amendments; legume integration in the production system; and combined inorganic and organic inputs. Research is required to identify inputs that help meet both nutrients availability while contributing to SOC build up at the same time.