Organic matter management for soil conservation and productivity restoration in Africa: A contribution from Francophone research
This paper reviews and synthesizes studies on the effects of erosion on grain crop productivity in Rwanda, Cameroon, Burkina Faso and Burundi. While soil conservation practices are effective in reducing soil erosion, these strategies alone are often insufficient for boosting yields due to nutrient deficiencies. In Rwanda hedges substantially reduced erosion (less than 2 t ha(-1) y(-1) compared to 250 t for traditional cropping systems and 500 t for bare fallow). However, because of insufficient soil P, there were no increases in yields without mineral fertilizer. Likewise, in Nigeria a living hedge treatment showed very low run-off and erosion rates, but N fertilization was needed to see any increase in productivity. On a banana plantation in Burundi, both tree canopy and mulch cover reduced erosion. Full mulching showed the greatest decrease in erosion and also maintained good water infiltration. Once the soil was eroded, it could not be restored to its original productivity and character, even with the addition of amendments. Field trials in Cameroon revealed an increase in erosion corresponding to an increase in tillage intensity. Grass mulch effectively decreased erosion and run-off.