Effect of biomass management regimes and wetting-drying cycles on soil carbon mineralization in a Sudano-Sahelian region

In Sudano-Sahelian regions, wetting-drying cycles may affect soil carbon mineralization in soil already poor in carbon. Conservation agriculture systems by improving crop residues return to soil is given to increase soil organic carbon and soil fertility. We studied the effect of biomass management regimes and wetting-drying cycles on soil carbon stocks and mineralization. A 50-day experiment was set up to compare carbon mineralization under two biomass management regimes, with and without mulch, using three soil wetting treatments. Wetting the soil and mulching increased soil carbon mineralization. However, wetting-drying cycles did not increase the soil carbon mineralization as compared with soils kept moist. During the experiment, the total carbon mineralization from the dry soils was low, 0.63 tC ha−1 and 0.53 tC ha−1 respectively for soils with and without mulch. Total carbon mineralization from soil without mulch was 1.40 tC ha−1 with wetting-drying cycles and 1.51 tC ha−1 for soils that were kept moist. Total carbon mineralization from soils with mulch was 1.70 tC ha−1, regardless of whether the soils had wetting-drying cycles or were kept moist. In our context, characterized by very little crop residues and rapid mineralization of this biomass, the conservation agriculture systems do not seem sufficient to increase soil organic carbon stocks.