Wetting-drying cycles do not increase organic carbon and nitrogen mineralization in soils with straw amendment

摘要

Increasing soil organic matter (SOM) is of primary importance for maintaining soil fertility and mitigating climate change. Leaving crop residues on top of soil is not always an efficient means of increasing SOM because (i) of the high mineralization of the crop residues, (ii) crop residues may increase the mineralization of existing SOM (priming effect) and (iii) wetting-drying cycles may increase mineralization of SOM and crop residues. Little research has been carried out into these mechanisms under Sudano-Sahelian conditions where the rainfall is mostly irregular with wetting-drying cycles during the transition between the wet and the dry season. To evaluate the effect of wetting-drying cycles on the mineralization of SOM and crop residues and the priming effect, an agricultural soil from the North Region of Cameroon with or without (controls) C-13-labeled rice straw amendment as crop residues was either subjected to five wetting-drying cycles or maintained at constant water potential after a single rewetting event. Soil samples were incubated for 70 days at 28 degrees C and the CO2 and (CO2)-C-13 emissions and mineral N were monitored.