Controlled release urea combined with normal urea (CRUNU) can potentially improve crop yields and reduce the associated environmental risk. However, the effects of CRUNU on farmland environmental benefits and the agroecosystem nitrogen (N) balance have not been evaluated in the winter wheat–summer maize multiple cropping system in northwest China, and few studies have quantified the impacts of CRUNU on N losses with this cropping system based on life cycle assessment. Therefore, we performed a field experiment for two years during 2020–2022 with two types of N fertilizer (normal urea (NU) and CRUNU) and at three N application rates (low: 135 kg N ha–1, medium: 180 kg N ha–1, and high: 225 kg N ha–1) at Caoxinzhuang experimental farm to comprehensively evaluate the effects of CRUNU on the agronomic, N balance, environmental, and economic benefits in winter wheat–summer maize cropping. Compared with NU, CRUNU helped to synchronize the N supply and demand for wheat and maize, and under all three N application rates, the annual average grain yield and grain N uptake increased with CRUNU, as well as reducing the volatilization of NH3 by 16.69 %, N2O emissions by 25.16 %, and N losses due to nitrate (NO3–) leaching by 44.23–61.65 %, thereby maintaining the total N storage. Considering both the N input and output, CRUNU achieved a lower N surplus than NU and maintained the N balance in the farmland ecosystem. In addition, CRUNU significantly reduced the reactive N losses at the three N application rates to decrease the N footprint (NF) by 25.48–42.85 %, where CRUNU obtained the lowest NF at the medium N application rate. More importantly, the benefits of CRUNU for increasing the grain yield at different N application rates offset the higher agricultural input costs and reduced the environmental costs due to N2O emissions, NH3 volatilization, and NO3– leaching losses, so the net benefits increased by 23.14–29.25 %. Furthermore, the net benefits under CRUNU did not differ significantly at the medium and high N application rates. Therefore, we recommend CRUNU application at the medium rate as an effective strategy for improving the N balance, environmental effects, and economic benefits in wheat–maize multiple cropping systems

中文翻译：

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控释尿素与普通尿素结合可维持小麦-玉米复种的氮平衡，提高环境和经济效益


控释尿素与正常尿素 （CRUNU） 相结合可能会提高作物产量并降低相关的环境风险。然而，在西北地区冬小麦-夏玉米复种制度中，CRUNU对农田环境效益和农业生态系统氮素（N）平衡的影响尚未得到评价，很少有研究基于生命周期评价量化CRUNU对该种植制度氮损失的影响。因此，我们在 2020-2022 年期间在草心庄实验场进行了为期两年的田间试验，使用两种氮肥（普通尿素 （NU） 和 CRUNU）和三种施氮量（低：135 kg N ha–1、中：180 kg N ha–1 和高：225 kg N ha–1）在草心庄实验场进行了为期两年的田间试验，以综合评价 CRUNU 对农艺的影响， 冬小麦-夏玉米种植的氮平衡、环境和经济效益。与 NU 相比，CRUNU 有助于同步小麦和玉米的氮供需，在所有三种施氮量下，CRUNU 的年平均粮食产量和粮食氮吸收量增加，NH3 的挥发量减少了 16.69 %，N2O 排放量减少了 25.16 %，硝酸盐 （NO3–） 浸出引起的氮损失减少了 44.23–61.65 %， 从而保持总 N 存储。考虑到氮的投入和产出，CRUNU 实现了低于 NU 的氮盈余，并保持了农田生态系统的氮平衡。此外，CRUNU 显著降低了三种氮施用量下的反应性氮损失，将氮足迹 （NF） 减少了 25.48-42.85 %，其中 CRUNU 在中等氮施用量下获得了最低的 NF。 更重要的是，CRUNU 在不同施氮量下提高粮食产量的好处抵消了较高的农业投入成本，并降低了由于 N2O 排放、NH3 挥发和 NO3 浸出损失而造成的环境成本，因此净收益增加了 23.14-29.25%。此外，CRUNU 下的净收益在中高氮施用量下没有显著差异。因此，我们建议以中等剂量施用 CRUNU 作为改善小麦-玉米复种制度氮平衡、环境影响和经济效益的有效策略