SOIL NITROGEN CYCLING AND ENVIRONMENTAL IMPACTS IN THE SUBTROPICAL HILLY REGION OF CHINA: EVIDENCE FROM MEASUREMENTS AND MODELING
Jianlin Shen, Yong Li, Yi Wang, Yanyan Li, Xiao Xiang Zhu, Wenqian Jiang, Yuyuan LI, Jinshui Wu
Abstract
<List> <ListItem><ItemContent> ● Soil nitrogen fluxes and influencing factors were reviewed in the subtropical hilly regions. </ItemContent></ListItem> <ListItem><ItemContent> ● Fertilizer application and atmospheric deposition contributed largely to soil nitrogen input. </ItemContent></ListItem> <ListItem><ItemContent> ● High gaseous, runoff and leaching losses of soil nitrogen were measured. </ItemContent></ListItem> <ListItem><ItemContent> ● Soil nitrogen cycles are well modelled with the Catchment Nutrients Management Model. </ItemContent></ListItem></List> The subtropical hilly region of China is a region with intensive crop and livestock production, which has resulted in serious N pollution in soil, water and air. This review summarizes the major soil N cycling processes and their influencing factors in rice paddies and uplands in the subtropical hilly region of China. The major N cycling processes include the N fertilizer application in croplands, atmospheric N deposition, biological N fixation, crop N uptake, ammonia volatilization, N<sub>2</sub>O/NO emissions, nitrogen runoff and leaching losses. The catchment nutrients management model for N cycle modeling and its case studies in the subtropical hilly region were also introduced. Finally, N management practices for improving N use efficiency in cropland, as well as catchment scales are summarized.