Adding a soil fertility dimension to the global farming systems approach, with cases from Africa

The global farming systems (GFS) approach is extended by adding a soil fertility and nutrient management dimension for Africa's forest-based, maize mixed, cereal–root crop mixed, and agro-pastoral millet/sorghum farming systems. Use is made of sustainable livelihood concepts, translated into farmer capitals (natural, physical, financial, human, social), and the indicator-based DPSIR (driving force-pressure-state-impact-response) framework for environmental reporting. State and impact indicators show, for each GFS, levels of nutrient stocks and flows, respectively. In case of nutrient depletion, soils may (i) initially still be fertile enough to provide reasonable and stable yields, (ii) support declining yields, or (iii) support low yields at low fertility level. In the latter case, food security is generally at stake. Response indicators include the level of uptake of improved integrated nutrient management strategies at land user level, and the enforcement of new and enabling pro-agriculture and pro-environment policies. Although the extended GFS have no direct relevance for farm-level interventions, the approach can be used to frame soil fertility research priorities and policies at a regional level.