Spatial variability and drivers of N2O emission responses to nitrogen fertilization across agricultural regions in China

Abstract

Nitrogen fertilization is an important source of agricultural N 2 O emissions, yet the spatial variability in nitrogen-induced N 2 O responses and its underlying drivers across agricultural regions in China remain insufficiently understood. This study conducted a meta-analysis of 462 independent field observations from 83 studies to quantify the responses of cropland N 2 O emissions to nitrogen fertilization across seven agricultural regions in China and to examine the associated environmental and management factors. Nitrogen fertilization significantly increased N 2 O emissions, with a pooled lnRR of 1.22 (95% CI: 1.08–1.36), corresponding to a 237.8% increase relative to unfertilized controls, while substantial heterogeneity was observed among observations. The magnitude of N 2 O responses differed significantly among agricultural regions, with the highest response in the Huang-Huai-Hai Plain (lnRR = 1.63) and the lowest in the Northern arid and semiarid region (lnRR = 0.86), although substantial heterogeneity remained within regions. Subgroup analyses indicated that nitrogen application rate, fertilizer type, cropping system, precipitation, temperature, and soil texture were associated with differences in N 2 O responses. In multivariable meta‑regression, nitrogen application rate exhibited a significant nonlinear association with N 2 O responses, while significant interactions among nitrogen application rate, soil pH, precipitation, and fertilizer type suggested that N 2 O responses were jointly modulated by environmental and management conditions rather than driven by independent main‑effect controls. These findings suggest that agricultural regionalization can capture broad-scale spatial differentiation in nitrogen-induced N 2 O responses, yet substantial within‑region heterogeneity highlights that agricultural regions should not be treated as homogeneous response units, and local environmental and management conditions must be considered when assessing these responses.