Lower nitrogen recovery efficiency (NRE) and negative environmental impacts caused by excessive nitrogen (N) fertilization threaten the sustainability of agriculture. Efficient and appropriate fertilization practices are extremely important to achieve higher crop yield with minimum N loss. A field microplot experiment was conducted in a wheat-maize rotation system in Shaanxi province, at North China Plain, using the ¹⁵N isotope tracer technique to qualify the different annual N managements in terms of crop yield, NRE, N distribution in plant-soil, and N losses to optimize the N management. The experiment included four N treatments: conventional practice with 510 kg ha⁻¹ annually in four applications (N1), and three optimized N treatments, reducing N rate to 420 kg ha⁻¹, adjusting topdressing fertilizer times and using slow-release fertilizer (SRF) (N2, N3, N4). The results showed that the grain yield and N uptake did not differ significantly among treatments. N from fertilizer taken up (Ndff) by wheat was not affected by N management; however, in maize, Ndff performed differently. Optimized treatments significantly decreased the Ndff as compared to N1 treatment. Furthermore, NRE of wheat and annual nitrogen recovery efficiency (annual NRE) did not differ among treatments in 2016 but significantly increased in 2017 compared to N1. Annual NRE in 2017 was similar to that obtained for wheat. For maize, optimized N managements decreased the NRE in N3 and N4 treatments of two years. Potential losses in wheat were also similar amongst treatments, but in maize, N3 and N4 had lower residual N in the soil’s top 60 cm but resulted in higher potential losses than N1 and N2. Overall, our results demonstrate that applying 420 kg N ha⁻¹ annually in three applications and combining SRF and urea are effective to sustain crop yield, improve the efficiency of N usage by maize, and reduce N losses in this region.

中文翻译：

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影响15N标记肥料命运的冬小麦-夏玉米轮作最佳氮肥施用方式

较低的氮回收效率（NRE）以及因过量施氮导致的负面环境影响威胁着农业的可持续性。高效而适当的施肥方法对于以最小的氮损失实现更高的作物产量至关重要。使用¹⁵ N同位素示踪技术，在华北平原陕西省小麦-玉米轮作系统上进行了田间微图试验，以验证作物产量，NRE，植物土壤中氮的分配方面不同的年度氮管理和N损失以优化N管理。实验包括4种N处理：常规实践，每年在4种应用（N1）中使用510 kg ha ^-1，以及3种优化的N处理，将N含量降低至420 kg ha ^-1，调整追肥时间并使用缓释肥料（SRF）（N2，N3，N4）。结果表明，不同处理之间的籽粒产量和氮素吸收没有显着差异。小麦吸收的肥料中的氮（Ndff）不受氮管理的影响；但是，在玉米中，Ndff表现不同。与N1处理相比，优化处理显着降低了Ndff。此外，与N1相比，2016年不同处理的小麦NRE和年度氮回收效率（年度NRE）没有差异，但2017年显着提高。2017年的年度NRE与小麦相似。对于玉米，优化的氮管理降低了两年的N3和N4处理的NRE。小麦的潜在损失在处理之间也相似，但在玉米中，N3和N4在土壤表层60 cm的残留N较低，但导致的潜在损失高于N1和N2。总体而言，我们的结果表明，施用420 kg N ha在三个应用中，每年^-1并结合使用SRF和尿素可有效维持作物产量，提高玉米对氮的利用效率并减少该地区的氮损失。