How are annual CH4, N2O, and NO emissions from rice-wheat system affected by nitrogen fertilizer rate and type?

Although the effect of controlled-released fertilizer (CRF) on methane (CH4) and nitrous oxide (N2O) emissions has been investigated from many rice-wheat rotation systems, most studies were conducted either in the rice or in the wheat seasons. Few studies measured CH4, N2O, and nitric oxide (NO) emissions from rice-wheat rotation systems simultaneously. In this study, one-year outdoor pot experiments and two-year field experiments were conducted to investigate the effects of altering nitrogen (N) fertilizer type from traditional fertilizer (TF) (e.g., compound fertilizer and urea) to CRF and reducing 30% of the local conventional N application rate on CH4, N2O, and NO emissions from a typical Chinese rice-wheat rotation system. Results showed that the annual cumulative N2O emissions and EFN2O in the CRF treatment decreased by 3.91%-16.7% and 9.23%-20.7% compared with the TF treatment, respectively. These emissions also significantly decreased by 26.0%-34.4% and 18.1%-28.5% when local conventional N fertilizer application rate was decreased by 30% (P < .05). However, neither altering fertilizer type nor reducing 30% N fertilizer application rate affected CH4 emissions (P > .05), and the reduction effect of CRF on NO emissions could only be detected at the CRF fertilization rate at 270 kg N ha(-1) per season but not at 190 kg N ha(-1) per season. The annual total global warming potential in CRF treatment decreased by approximately 1.47%-9.17% compared with that in TF treatment. Moreover, this potential decreased by 8.29%-15.4% when 30% of the N application rate was reduced. Therefore, altering N fertilizer type from TF to CRF and applying optimal N rate should be encouraged as a partial substitution N fertilizer management strategy for the sustainable development of rice-wheat rotation systems.