Nitrogen use efficiency exhibits a trade-off relationship with soil N2O and NO emissions from wheat-rice rotations receiving manure substitution

Abstract

Nitrogen (N) fertilizer has shown to affect soil nitrous oxide (N2O) and nitric oxide (NO) emissions that contribute to global warming and stratospheric ozone depletion. However, soil N2O and NO emissions with a linkage to crop N use efficiency (NUE) under different fertilization strategies in winter wheat-summer rice rotation systems remain yet to be further examined. Here, we carried out a two-year field study to assess the response of soil N2O and NO emissions as an interplay with NUE to different fertilization strategies in a typical winter wheat-summer rice rotation cropland of subtropical China. Three fertilizer treatments were established consisting of phosphorus (P) and potassium (K) fertilizer application (PK), NPK fertilizer application (NPK), and NPK fertilizer application with N partially replaced with manure (NPKM). Annual N2O, NO and N2O + NO emissions averaged 0.96, 0.24 and 1.19 kg N ha−1 yr−1 for the PK plots and 6.54, 1.48 and 8.03 kg N ha−1 yr−1 for the NPK plots, respectively. Relative to the NPK plots, partially replacing chemical N fertilizer with manure decreased annual N2O and NO emissions and their combined emissions by 13–15%, while it significantly enhanced crop NUE as compared to the NPK plots. Annual mean emission factors (EFs) of N fertilizer for N2O and NO were estimated to be 1.17% and 0.26% for the NPK plots, and 0.99% and 0.22% for the NPKM plots, respectively. Both N2O and NO emissions were positively correlated with N surplus, while yield-scaled N2O + NO emissions and the fertilizer N-induced combined EF for N2O + NO were negatively related to crop NUE. Together, our results highlight that improving crop NUE while reducing soil N surplus constitutes an effective strategy to mitigate soil gaseous N loss through N2O and NO in the wheat-rice rotation cropping systems.