Targeting resources within diverse, heterogeneous and dynamic farming systems: Towards a ‘uniquely African green revolution’

Smallholder farms in sub-Saharan Africa (SSA) are highly diverse and heterogeneous, often operating in complex socio-ecological environments. Much of the heterogeneity within the farming systems is caused by spatial soil variability, which results in its turn from the interaction between inherent soil/landscape variability and human agency through the history of management of different fields. Technologies and resources designed to improve crop productivity often generate weak responses in the poorest fields of smallholder farms. Thus, options for soil fertility improvement must be targeted strategically within heterogeneous farming systems to ensure their effectiveness and propensity to enhance the efficiency of resource (e.g. land, labour and nutrients) use at farm scale. Key issues in design of approaches for strategic targeting of resources include (1) inherent soil variability across agroecological gradients; (2) social diversity, farmers’ production orientations and livelihood strategies; (3) farmer-induced gradients of soil fertility, their causes and consequences of efficient allocation of scarce resources; (4) competing objectives and trade-offs that farmers face between immediate production goals and long-term sustainability and (5) the complexity of farmers’ own indicators of success. We used an analytical framework in which systems analysis is aided by survey, experiments and simulation modelling to analyse farming futures in the highlands of East Africa. Our work contributes to the development of ‘best-fit’ or tailor-made technologies, using combinations of mineral fertilizers and organic matter management from N2-fixing legumes and animal manures. Thus, we hope to contribute to the design of a ‘uniquely African green revolution’ called for by UN Director General Kofi Annan, which fits technology interventions to the diverse and heterogeneous smallholder farming systems of sub-Saharan Africa