Jianbin Zhou1, Bin Liang1,2, Wei Zhao1, 3, Mengjie Xia1, Xueyun Yang1
1College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China;
Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, Yangling, Shaanxi 712100, China
2College of Resources and Environmental Sciences, Qingdao Agriculture University, Qingdao, Shandong 266109, China
3Weinan Agricultural Technology Extension Service Center, Weinan, Shaanxi 714000, China
About one third of nitrogen (N) fertilizer is retained in the soil after crop harvest. Understanding the fate of this residual fertilizer N in soil is important for evaluating its overall use efficiency and environmental effects. In this study, the 15N-labelled fertilizer was applied to winter-wheat growing in three different fertilizedsoils (No-F, no fertilizer; NPK, inorganic NPK fertilization; and MNPK, manure plus inorganic NPK fertilization) from a long-term trial (19-year) on the south edge of the Loess Plateau, China. The fate of residual 15N in soils over summer fallow and the second winter-wheat growing season was followed. The amount of the residual N in the No-F soil was significantly higher than that in the NPK and MNPK soils after harvesting the first wheat crop. The forms of the residual N in the No-F soil was mainly in mineral form; and for the NPK and MNPK soils, they were mainly in organic form. The loss of 15N in No-F soil over the summer fallow was as high as 33%, and significantly higher than that in the NPK soil (8%) and MNPK soil (5%). The residual 15N use efficiency by the winter-wheat in the second cropping were equivalent to 9.0%, 2.0% and 2.2% of the originally applied 15N. A high proportion of the residual 15N was lost during the summer fallow in dryland farming. Better management of the residual N in soil during the summer fallow is required, its contribution to subsequent cropsis also deserved consideration when makingN fertilizer recommendation.