Weakened growth of cropland N2O emissions in China associated with nationwide policy interventions

China has experienced a rapid agricultural development over the past decades, accompanied by increased fertilizer consumptions in croplands, but the trend and drivers of the associated nitrous oxide (N2O) emissions remains uncertain. The primary sources of this uncertainty are the coarse spatial aggregation of agricultural activity data and the incomplete model representation of N2O emissions in response to management. Here we provide a data-driven estimate of cropland N2O emissions across China from 1990 to 2014, compiled using global monitoring network, nationwide survey-based reconstruction of N-fertilization and irrigation, and an updated version of a spatially-referenced nonlinear algorithm. In addition, we have evaluated the drivers behind changing cropland-N2O patterns using an index decomposition analysis approach. We find that China's annual cropland-N2O emission increased on average by +11.2 Gg N yr-2 (P < 0.001) from 1990 to 2003. After that, coincident with an ensemble of process-based land-surface models (LSMs), such increase seems to have diminished until 2014 (+2.8 Gg N yr-2, P = 0.02). The slowdown after 2003 was pervasive across the majority of croplands, accounting together for ~2/3 of total sowing areas. This change was mainly driven by the nationwide improvement (reduction) of N-fertilizer application rates, partially due to the prevalence of the Nationwide Soil Testing and Formulation Fertilization Program launched in the early 2000s; this reduction has almost offset the policy-driven expansion of sowing areas in major cropping regions, particularly the Northeast Plain and the lower Yangtze Basin. Our results underline the importance of high-resolution activity data and of spatially-explicit response of N2O emission to management for capturing cropland-N2O emission patterns. Improving the representation of nationwide policy intervention in LSMs are also recommended for future projections.