Spatiotemporal intensification of net anthropogenic nitrogen input driven by human activities in China from 1990 to 2020.

• The NANI peaked in 2020, representing a 54.41% increase compared to 1990. • The proportion of food/feed nitrogen input to NANI was the highest, reaching 62.30%. • The spatial pattern of NANI exhibited a decreasing trend from east to west and from north to south. • The spatiotemporal changes of NANI are related to the intensity of human activities. • Population density and GDP were the most influential socioeconomic factors impacting NANI. The issue of global nitrogen overload is widely acknowledged as a pressing concern, with excessive nitrogen input resulting from human activities posing a significant threat to regional security. Notably, China emerges as a prominent contributor, exhibiting one of the highest anthropogenic nitrogen inputs worldwide. This study employs the Net Anthropogenic Nitrogen Input (NANI) as a pivotal tool to scrutinize the spatial and temporal patterns of nitrogen input in China spanning from 1990 to 2020. The total NANI reached its zenith in 2020 at 723,378.80 kg·km−2·yr−1, marking a noteworthy 54.41 % increase from 1990. Among the various nitrogen sources, food/feed nitrogen input prevails, constituting 62.30 % of NANI, followed by atmospheric nitrogen deposition at 30.05 %. In less developed regions, primary contributors to NANI include nitrogen fertilizer application and crop nitrogen fixation. The spatial distribution of NANI exhibits a diminishing trend from east to west and north to south. Conducting a quantitative analysis, this study elucidates the impact of socioeconomic factors on NANI in China. Population density (r = 0.97) and GDP (r = 0.91) emerge as primary influencers, with agricultural factors such as livestock breeding (r = 0.70), grain production (r = 0.40), and fertilizer application (r = 0.65) following suit. In addressing the environmental challenges posed by excessive nitrogen, future mitigation strategies should prioritize enhancements in manure management practices and the implementation of pollution reduction facilities. [ABSTRACT FROM AUTHOR]