Modeling impacts of alternative farming management practices on carbon sequestration and mitigating N₂O emissions from spring maize fields

Spring maize is one of the largely grown crops in Northeast China. The spring maize fields may become an important emission source of greenhouse gases due to continuous tillage and overuse of nitrogen fertilizer. Reducing emissions of greenhouse gases and maintaining crop yields by optimizing farming management practices have a crucial meaning for ensuring sustainable maize production systems. Denitrification-Decomposition (DNDC) model is an effective tool in evaluating the mitigation of greenhouse gases. In this study, the DNDC model was verified; the long-term impacts of alternative management practices on maize production and the emissions of carbon dioxide (CO2) and nitrous oxide (N2O) were assessed using this model at the same time. The results indicated that the simulations of maize yields and seasonal accumulation of soil respirations and N2O emissions were consistent with the data observed. The DNDC can generally capture the temporal pattern of daily soil respirations and N2O emissions. The modeled impacts on alternative fertilization and crop residue management practices were summarized by the following: 1) optimizing N fertilization application could slightly decrease the emissions of greenhouse gases by 8%-13%, and maintain maize yields; 2) optimizing N fertilization in combination with crop straw amendment has significant potential effect in decreasing emissions of greenhouse gases and maintaining maize yields. This modeling study can provide useful information on the optimization for farming management practices and on maintaining effective carbon fixation and emission reduction in the system of spring maize production in Northeast China