Classifying, monitoring and improving soil nutrient stocks and flows in African agriculture

Nutrient stocks and budgets (positive minus negative flows) are quantifiable indicators of sustainability, and are applied in this paper to classify agro-ecosystems. Earlier work revealed that most agricultural systems in sub-Saharan Africa (SSA) can be labelled nonsustainable due to low nutrient stocks and negative nutrient budgets. To increase production and build sustainable agro-ecosystems in SSA, technologies that rank under "integrated nutrient management" (INM) should be adopted, to save nutrients from being lost, and to add new nutrient supplies to the system. An account is given of the socioeconomic factors at national and farm level, the interplay of which determines the actual adoption rate of INM. Based on an overview of what we do know and what we don't know, an INM research agenda is proposed that is based on the knowledge gaps.