Fates of 15N-urea in black soil – maize system and their response to straw incorporation in northeast China: a case study

Zhi Quan1, Shanlong Li1, Feifei Zhu1, Yunting Fang1, *, Peipei Li2, Limei Zhang2, Rong Sheng3, Wenxue Wei3, Jizheng He2

1Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China

2State Key Laboratory of Urban and Regional Ecology, Research Centre for Eco-environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China

3Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China

*Correspondence: fangyt@iae.ac.cn,




A better understanding of the fates of fertilizer N is critical to design appropriate N management strategies in intensively cultivated croplands. In this study, we evaluated the fates of 15N-urea in a field experiment on a black soil-maize system and their responses to straw incorporation in Gongzhuling, Northeast China. In order to get realistic results, we adopted the field management used by local farmers. Results showed that the crop N uptake was the main sink, recovering 52-53 % of the fertilizer N. Total 15N recoveries in plant organs followed the order: grain (27-29%) > leaf (11-12%) > stem (6%) > tassel, silks, leaf sheath, husks, etc. (5%) > root (2%) > cob (1%). Tracer N remaining in soil was the second largest sink (25-33%), and most (18-29%) was located in the ridge 0-20 cm layer (fertilized area). The total loss of fertilizer N was 13-23%. Straw incorporation increased the retention of applied fertilizer N and decreased its losses, although there was no significant difference in  plant N uptake. The contribution of fertilizer N to total  N uptake was 36-37% at the physiological maturity stage of maize. Fertilizer N was an important N source for maize growth but soil N was still the main N source. Our results indicate that Nitrogen Use Efficiency (NUE) in maize cultivation system in northeast China is not as low as that reported by many previous studies using difference or balance method. Considering the low NUE in China, our next aim is to find out which region, and which kinds of crops lowered the overall NUE in Northeast China.