National assessment of nitrogen fertilizers fate and related environmental impacts of multiple pathways in China.

Managing excess nitrogen (N) fertilizers remains a major obstacle to improving crop growth and environmental sustainability. To provide information for more quantitative N management, N use efficiency (NUE f) and N emissions ratio of fertilizer (NER f) in China were estimated at high resolution from 2004 to 2017. A descriptive variable (H/E value) was utilized to determine the fate of N fertilizers between crop production and the consequent N emissions. Furthermore, the related environmental impacts, in terms of water pollution relating to surface runoff and leaching, global warming and acidification effect, were analyzed in this study. The results indicated although NUE f had increased from 21.61% to 26.47%, it was still much lower than that of developed countries due to regional imbalance in China. Accordingly, the emissions of N fertilizers were estimated as 18.52%–24.75% at high resolution across China. Those higher H/E values were observed in the northeastern and eastern China, indicating that these two regions had effective agricultural production. However, the water pollution caused by N fertilizers was in the northern part of China due to the shortage of water resources, while Yangtze River delta, Lianghu Plain, Yungui Plateau and Pearl River Delta had been identified as the hotspots of global warming and acidification effect due to abundant water system and rice cultivation. Consequently, it was suggested that different N management strategies should be developed by considering particular environmental impacts and simultaneously achieving sustainable agricultural development. Image 1 • The comprehensive fate of N fertilizer was evaluated at the national scale. • Multiple loss pathways of N fertilizer were compared at high resolution. • Spatial-temporal variability of the fate of N fertilizer was identified. • Hotspots for environmental impact of multi-pathways loss were identified. • It was found that 18.52%–24.75% of N fertilizer was loss to the environment. [ABSTRACT FROM AUTHOR]