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ABSTRACT Ammonia‐oxidising microorganisms play a central role in regulating N 2 O production in dryland soils. However, the spatial variation in the contribution of the nitrification pathway (NP) to total N 2 O emissions, as well as its associations with ammonia‐oxidising archaea (AOA) and bacteria (AOB), remains insufficiently characterised. Using an 11‐year tillage experiment (zero ZT and chisel plough CPT vs. conventional plow tillage PT), we quantified the NP contribution to total N 2 O emissions and elucidated the respective roles of AOB and AOA in dryland agroecosystems. Long‐term implementation of conservation tillage significantly reduced the proportion of nitrification‐derived N 2 O in total N 2 O emissions. Compared to PT, NP‐associated N 2 O fluxes under CPT and ZT were reduced by 59.32% and 34.78%, respectively. In addition, during the peak N 2 O emission period, ZT and CPT decreased the AOA : AOB ratio while increasing the richness, diversity, and evenness of AOA and AOB communities. The contribution of deterministic assembly processes within the AOA community progressively increased with greater tillage intensity. By contrast, during the peak N 2 Oemission period, deterministic assembly exerted a stronger imprint on AOB communities under conservation tillage than under plough‐tilled soil. Partial least squares path modelling identified soil moisture at 10 and 20 cm depths, NO 3 − concentration, soil pH, AOA abundance and the AOA : AOB ratio as the major variables regulating NP‐derived N 2 O emissions. Long‐term conservation tillage significantly decreased NP‐derived N 2 O emissions by lowering the AOA : AOB ratio and enriching keystone taxa within the microbial co‐occurrence network. These results provide a promising conservation tillage strategy that effectively improves soil nitrogen retention, enhances the basic soil fertility and maintains the sustainable productivity in dryland farmland.
Yuan et al. (2026) studied this question.