Developing Sustainable Conservation Agriculture for Smallholder Farmers In Southern Africa.

Conservation agriculture systems are complex production systems that must be adapted to the local ecosystem.  Many common African cropping systems are tillage intensive and highly unsustainable both from a soil loss (>100 ton/ha annual loss) and crop yield (maize yields of <1 ton/ha) perspectives.  The objectives of this research were to develop sound N, P and K fertilizer recommendations, determine optimum plant populations, evaluate the utility of various cover crops to reduce weed pressure from winter annual weeds, and to determine the relative C sequestration rates on soils farmed using no-till practices.  Our results suggest that approximately 100-60-30 of N-P-K are needed per hectare to produce more than 5 t/ha maize, that the optimal plant population for maize is approximately 44,000 plants per hectare, that cover crops are reducing weed infestations by winter annuals by approximately 90%, and that the C sequestration rates on no-till soils are approximately 300 kg C per hectare per year.  These results suggest that solid agronomic practices improve local food security and provide global mitigation of greenhouse gases.