Nitrogen (N) management in cropping systems needs adjustments because constraints to crop production are mostly related to high inputs and low recovery of N fertilizers. We used the DayCent model to predict regional N inputs, outputs, and balances of Swiss soils under (1) a range of N fertilizer input levels (0–300% of recommended crop-specific rates) and (2) organic fertilization, reduced tillage or cover cropping at the recommended input of N. The crops included wheat, maize, and root/tuber crops and legumes. Decreasing N inputs reduced the environmental impact by 13.5–51.3 kg N ha\(^{-1}\), but it also reduced the yield by 6.8–44.8 kg N ha\(^{-1}\). Increasing N inputs led to an increase in yield by 5.6–29.5 kg N ha\(^{-1}\), but with additional losses of 14.9–181.8 kg N ha\(^{-1}\) into the environment. Harvested crop N and \(\hbox {NO}_3^{-}\) leaching accounted for 30–59% and 27–62% of fertilizer-derived changes in total N output, respectively. Converting conventional to organic cropping led to a mean increase in soil N balance by 0.3–62.6 kg N ha\(^{-1}\). The soil N balance increased the most by using partially decomposed organic fertilizer in combination with cover cropping and reduced tillage. However, this positive N balance was mainly due to a reduction in N removal with harvest and \(\hbox {NO}_3^{-}\) leaching. The use of highly decomposable organic matter and cover cropping did not lead to any N yield penalty while decreasing \(\hbox {NO}_3^{-}\) leaching. These results highlight that organic practices combined with reduced tillage and cover cropping can optimize the use and recovery of N resources.

中文翻译：

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瑞士农田中区域土壤氮平衡的模拟

种植系统中的氮管理需要调整，因为对作物生产的限制主要与氮肥的高投入和低回收率有关。我们使用DayCent模型来预测瑞士土壤在（1）一定范围的氮肥投入水平（建议的作物特定比例的0–300％）和（2）有机肥，减少耕种的情况下区域氮的输入，输出和平衡或以推荐的氮输入覆盖种植。作物包括小麦，玉米和块根/块茎作物和豆类。氮素输入的减少使环境影响降低了13.5–51.3 kg N ha \（^ {-1} \），但也使产量降低了6.8–44.8 kg N ha \（^ {-1} \）。氮输入增加导致单产增加5.6–29.5 kg N ha \（^ {-1} \），但还会对环境造成14.9–181.8 kg N ha \（^ {-1} \）的额外损失。收获的作物氮素和\（\ hbox {NO} _3 ^ {-} \）的淋失分别占总氮素产量变化的30–59％和27–62％。从常规种植转为有机种植导致土壤氮平衡平均增加0.3–62.6 kg N ha \（^ {-1} \）。通过使用部分分解的有机肥结合覆盖作物和减少耕作，土壤氮平衡增加最多。但是，这种正的N平衡主要是由于收获和\（\ hbox {NO} _3 ^ {-} \）淋洗减少了N去除。使用高度可分解的有机物和覆盖作物并没有导致氮产量下降，反而降低了\（\ hbox {NO} _3 ^ {-} \）浸出。这些结果表明，有机做法与减少耕种和掩盖作物相结合可以优化氮资源的利用和回收。