Optimal N management affects the fate of urea-15N and improves N uptake and utilization of wheat in different rotation systems

• Published in: Frontiers in plant science Vol. 15; p. 1438215
• Main Authors: Ma, Quan, Dai, Dandan, Cao, Yifan, Yu, Qiaoqiao, Cheng, Xiyang, Zhu, Min, Ding, Jinfeng, Li, Chunyan, Guo, Wenshan, Zhou, Guisheng, Zhu, Xinkai
• Format: Journal Article
• Language: English
• Published: Frontiers Media S.A 25.07.2024
• Subjects: 15N-labeled urea; grain yield; N uptake and utilization; Plant Science; preceding crop; wheat
• ISSN: 1664-462X; 1664-462X
• DOI: 10.3389/fpls.2024.1438215

Rice-wheat and maize-wheat rotations are major cropping systems in the middle and lower reaches of Yangtze River in China, where high nitrogen (N) inputs and low N efficiency often exacerbate resource waste and environmental pollution. Due to the changes in factors such as soil properties and moisture content, the N fate and the N utilization characteristics of wheat in different rotations are significantly different. Efficient N management strategies are thus urgently required for promoting maximum wheat yield in different rotation systems while reducing N loss. A 2-year field experiment using isotopic ( 15 N) tracer technique was conducted to evaluate the fate of 15 N-labeled urea in wheat fields and the distribution characteristics of N derived from different sources. The wheat yield and N use efficiency under various N rates (180 and 240 kg ha −1 , abbreviated as N180 and N240) and preceding crops (rice and maize, abbreviated as R-wheat and M-wheat) were also investigated. The results showed that N240 increased N uptake and grain yield by only 8.77−14.97% and 2.51−4.49% compared with N 180, but decreased N agronomic efficiency (NAE) and N physiological efficiency (NPE) by 14.78−18.79% and 14.06−31.35%. N240 also decreased N recovery in plants by 2.8% on average compared with N180, and increased N residue in soil and N loss to the environment. Compared with that of basal N, the higher proportion of topdressing N was absorbed by wheat rather than lost to the environment. In addition, the accumulation of topdressing N in grain was much higher than that of basal N. Compared with that in R-wheat treatment, plants in M-wheat treatment trended to absorb more 15 N and reduce unaccounted N loss, resulting in higher yield potential. Moreover, the M-wheat treatment increased N recovery in 0−20 cm soil but decreased 80−100 cm soil compared with R-wheat treatment, indicating a lower risk of N loss in deeper soil. Collectively, reducing N application rate and increasing the topdressing ratio is an effective way to balance sustainable crop yield for a secure food supply and environmental benefit, which is more urgent in rice-wheat rotation.