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.