Enhanced nitrogen fertilizer combined with straw incorporation can reduce global warming potential with higher carbon sequestration in a summer maize-winter wheat rotation system

The combined effects of nitrogen (N) fertilizers and straw incorporation (SI) on GHG emissions, crop yields, and net ecosystem carbon budget (NECB) in summer maize-winter wheat rotation systems are still uncertain. We conducted a two-year field experiment to evaluate the effects of SI combined with different N fertilization practices on soil N2O emissions, ecosystem respiration (Re), NECB, grain yields, net global warming potential (NGWP), and greenhouse gas intensity (GHGI). In total, five treatments were considered, namely conventional urea-N application (FP), optimal urea-N fertilizer (OPT) with and without SI (S+OPT and OPT), and enhanced-efficiency N fertilizers (equivalent to OPT) with and without SI (S+EENF and EENF). The results showed significantly decreased average annual N2O emissions under the OPT and EENF treatments by 22.70 and 51.35% (P < 0.05), respectively, compared with that under the FP treatment. However, no significant differences in the annual Re emissions, NECB values, and crop yields were observed between the N fertilizer treatments (P > 0.05). The SI significantly increased the average annual N2O emissions, annual Re emissions, and annual grain yields by 36.01, 27.94, and 11.54% (P < 0.05), respectively, compared to no-straw treatments. The annual NECB values under the SI and no-straw treatments ranged from 1.19 to 1.94 t C ha(-1) yr(-1) and -1.89 to -1.19 t C ha(-1) yr(-1), respectively. The lower NGWP and GHGI values were observed in the S+EENF plots. The results suggest that the practice of enhanced-efficiency N fertilizers coupled with SI could improve crop yields and reduce NGWP and GHGI values in summer maize-winter wheat rotation systems.