Improving N cycling in agroecosystems is one of the key challenges in reducing the environmental footprint of agriculture. Further, uncertainty in precipitation makes crop water management relevant in regions where it has not been necessary thus far. Here, we focus on the potential of winter-killed catch crops (CCs) to reduce N leaching losses from N mineralization over the winter and from soil water management. We compared four single CCs (white mustard, phacelia, Egyptian clover and bristle oat) and two CC mixtures with 4 and 12 plant species (Mix4 and Mix12) with a fallow treatment. High-resolution soil mineral N (N_min) monitoring in combination with the modelling of spatiotemporal dynamics served to assess N cycling under winter-killed CCs, while soil water was continuously monitored in the rooting zone. Catch crops depleted the residual N_min pools by between 40 % and 72 % compared to the fallow. The amount of residual N uptake was lowest for clover and not significantly different among the other CCs. Catch crops that produce high N litter materials, such as clover and mustard leaves, showed an early N mineralization flush immediately after their termination and the highest leaching losses from litter mineralization over the winter. Except for clover, all CCs showed N_min values between 18 % and 92 % higher on the sowing date of the following maize crop. However, only Mix12 was statistically significant. Catch crops depleted the soil water storage in the rooting zone during their growth in autumn and early winter, but preserved water later on when their residues covered the ground. The shallow incorporation of CC residues increased water storage capacity during the cropping season of the main crop even under reduced soil water availability. Hence, catch cropping is not just a simple plant cover for the winter but improves the growth conditions for the following crop with decreased N losses. Mixtures have been shown to compensate for the weaknesses of individual CC species in terms of nutrient capture, mineralization and transfer to the following main crop as well as for soil water management. Detailed knowledge about plant performance during growth and litter mineralization patterns is necessary to make optimal use of their potential.

中文翻译：

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冬杀作物的土壤氮和水管理

改善农业生态系统中的氮循环是减少农业环境足迹的关键挑战之一。此外，降水的不确定性使得作物水分管理在迄今为止没有必要的地区具有相关性。在这里，我们关注冬季杀灭的捕捞作物 (CCs) 减少冬季氮矿化和土壤水分管理造成的氮淋失损失的潜力。我们比较了四种单一的 CC（白芥末、phacelia、埃及三叶草和刺毛燕麦）和两种 CC 混合物，分别含有 4 和 12 种植物（Mix4 和 Mix12）以及休耕处理。高分辨率土壤矿物质 N ( N _min) 监测与时空动力学模型相结合，用于评估冬季杀死的 CCs 下的 N 循环，同时在生根区持续监测土壤水分。 与休耕相比，捕捞作物消耗了 40% 至 72% 的剩余N _min库。三叶草的残余氮吸收量最低，其他CCs之间没有显着差异。三叶草和芥菜叶等产生高氮凋落物材料的作物，在它们终止后立即表现出早期的氮矿化冲刷，冬季凋落物矿化的浸出损失最高。除三叶草外，所有 CC 均显示N _min在下一个玉米作物的播种日期，该值高出 18 % 至 92 %。然而，只有 Mix12 具有统计学意义。捕获的作物在秋季和初冬生长期间耗尽了生根区的土壤蓄水量，但随后在其残留物覆盖地面时保留了水分。即使在土壤水分减少的情况下，CC 残留物的浅层掺入也增加了主要作物种植季节的蓄水能力。因此，捕捞作物不仅仅是冬季的简单植物覆盖，而是改善了下一个作物的生长条件，减少了氮损失。混合物已被证明可以弥补单个 CC 物种在养分捕获、矿化和转移到以下主要作物以及土壤水分管理方面的弱点。