PDF(Pubmed)
Abstract：
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 (15N) tracer technique was conducted to evaluate the fate of 15N-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 15N 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.
摘要：
水稻-小麦和玉米-小麦轮作是中国长江中下游的主要种植制度，高氮（N）输入和低氮效率通常会加剧资源浪费和环境污染。由于土壤特性和含水量等因素的变化，不同轮作小麦的氮素去向和氮素利用特性差异显著。因此，迫切需要有效的氮素管理策略，以提高不同轮作系统中小麦的最大产量，同时减少氮素损失。使用同位素（15N）示踪技术进行了为期2年的田间试验，以评估麦田中15N标记的尿素的命运以及来自不同来源的N的分布特征。在各种氮肥（180和240kgha-1，缩写为N180和N240）和先前作物（水稻和玉米，缩写为R-小麦和M-小麦）也进行了研究。结果表明，与N180相比，N240仅使N吸收和籽粒产量增加了8.77-14.97％和2.51-4.49％，但使N农艺效率（NAE）和N生理效率（NPE）降低了14.78-18.79％和14.06-31.35％。与N180相比，N240还使植物中的氮回收率平均降低了2.8％，并增加了土壤中的氮残留和环境中的氮流失。与基础氮相比，小麦吸收了较高比例的追肥N，而不是流失到环境中。此外,追肥N在籽粒中的积累远高于基础N。与R-小麦处理相比，M-小麦处理中的植物倾向于吸收更多的15N并减少不明原因的N损失，导致更高的产量潜力。此外，与R-小麦处理相比，M-小麦处理增加了0-20厘米土壤中的N恢复，但减少了80-100厘米土壤中的N恢复。表明在较深的土壤中氮素流失的风险较低。总的来说，减少氮肥施用量和提高追肥比例是平衡可持续作物产量、确保粮食供应和环境效益的有效途径。这在稻麦轮作中更为紧迫。
