Hungry Soils, Hungry People: Soil Management for Sustained Agricultural Production in Sub-Saharan Africa.

The ever declining per capita food production in Sub-Saharan Africa (SSA) continues to be a major challenge to the world’s scientific community. Over the past 40 years, efforts to increase agricultural productivity in the SSA had focused largely on the introduction of high yielding varieties (HYV), large scale mechanization and fertilizer application to crops, but this has not led to sustained crop production. Agricultural policies that have taken this path have left many farmers indebted. We conjecture that the lack of success is due to the low attention paid to soil management. Most tropical agricultural soils contain low organic matter; - the main energy source for soil processes and functioning. The soil organic matter declines rapidly upon cultivation and soil become degraded. The use of HYV and fertilizer application to crop grown on such soils is uneconomical. In this paper, we report on a 4-year study that investigated the combined effect of short-cycle residue production and retention as mulch, modest fertilizer application, and maize-fallow rotation on soil organic matter and maize yields in a forest farming zone of Ghana. Our results showed that this combination maintained the soil organic carbon near the initial pre-cultivation level of 18.0 g/kg throughout the study period and also maintained maize yields above 2.4 t/ha/yr, which was about three times the yield obtained under farmer practice. The use of HYV and fertilizer was only economical when the soil was adequately “fed” with residues. Residue removal was extremely detrimental to both the maintenance of soil organic matter and maize yield. By the end of the study, the organic carbon of residue removal treatments declined to 8.0 g/kg while the maize registered two yield failures. Future efforts to develop tropical agriculture need more focus on soil management than has hitherto been the case.