Abstract:

Legume-cereal intercropping systems with delayed nitrogen (N) application demonstrated multifunctional benefits, including enhanced soil quality, elevated crop productivity, and reduced carbon footprint. However, the microbial genetic mechanisms governing nitrous oxide (N 2 O) flux regulation under varied N postponement strategies remain inadequately quantified. Through a three-year field study (2019–2021) in Northwest China's arid irrigated region systematically investigated how N redistribution timing modulates N-cycling functional genes (ammonia-oxidizing archaea/bacteria amoA , denitrification-related nirS , nirK , and nosZ ) to mitigate N 2 O emissions in pea-maize polycultures. Employing a 3 × 3 factorial design combining cropping systems (intercropping, monocultures) with N management protocols (N1, 20% N fertilizer postponed, N2, 10% N fertilizer postponed, and N3, the traditional N fertilizer without postponing). N 2 O fluxes were reduced by 19.3% (pea) and 40.3% (maize) under N1 treatment relative to N3. The total N 2 O emissions in pea/maize intercropping under N1 was decreased by 27.5% compared to N3. Pearson correlation revealed N 2 O emissions positively related to N H 4 + – N , N O 3 − – N , archaea amoA (AOA), bacteria amoA (AOB), nirK and nirS , and was negatively correlated with soil labile organic matter (LOM) and nosZ gene abundance. Structural equation modeling identified that reduced AOB gene abundance correlates strongly with suppressed N₂O emissions (r = 0.30, p  < 0.05), suggesting its role as a key mediator. The optimal N1 strategy, involving 72 kg N ha⁻¹ reallocation from jointing to post-silking stages (15-day delay), effectively inhibited AOB-driven nitrification processes, thereby attenuating N 2 O generation. These findings establish strategic N postponement as an ecologically viable approach for dual productivity and emission control in sustainable intercropping systems.