Nitrogen (N) pollution from N inputs to agricultural soils contributes to widespread eutrophication and global climate change. One period susceptible to N losses is between winter grain harvest in summer and corn planting in spring in a corn-soybean-winter grain rotation. Cover crops used to immobilize N during this period often depend on tillage, which can exacerbate N losses. Therefore, we evaluated whether reduced-till cover crops could decrease nitrate (NO3 - ) leaching and nitrous oxide (N2 O) emissions during this period. We tested this strategy in a cropping systems experiment on a 4-ha plot in central Pennsylvania, USA over two years. This experiment compared a clover-timothy cover crop no-till underseeded into a standing spelt crop to a vetch-triticale cover crop established with tillage after spelt harvest. These systems were compared based on fortnightly N2 O emissions using static chambers (n = 4 per six sample dates) and potential NO3 - leaching using anion resin bags (n = 4 per system per year). Reduced-till cover crops minimized peak N2 O emissions during the fall compared to tilled cover crops. However, reduced-till cover crops did not decrease potentially leachable NO3 - relative to tilled cover crops despite decreases in soil inorganic N. Cover crop N isotopes revealed that clover N may have mineralized and leached over the winter. Our results suggest that reduced-till cover crops can decrease N2 O emissions to mitigate the climate impact of agriculture, but that winter hardy cover crops should be chosen to mitigate leaching. This article is protected by copyright. All rights reserved.

中文翻译：

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在冬季谷物中用播种不足的豆科草覆盖作物混合物减轻氮污染

从氮输入到农业土壤的氮 (N) 污染导致广泛的富营养化和全球气候变化。一个易受氮流失影响的时期是在玉米-大豆-冬粮轮作中的夏季冬粮收获和春季玉米种植之间。在此期间用于固定氮的覆盖作物通常依赖于耕作，这会加剧氮的损失。因此，我们评估了减耕覆盖作物在此期间是否可以减少硝酸盐 (NO3 - ) 浸出和一氧化二氮 (N2 O) 排放。两年多来，我们在美国宾夕法尼亚州中部 4 公顷的地块上进行的种植系统试验中测试了该策略。该实验将免耕种植的三叶草覆盖作物免耕种植成直立的斯佩尔特作物与在斯佩尔特收获后通过耕作建立的野豌豆-小黑麦覆盖作物。根据使用静态室（每六个样本日期 n = 4 个）和使用阴离子树脂袋浸出的潜在 NO3（每年每个系统 n = 4 个）的 N2 O 排放量，对这些系统进行比较。与翻耕覆盖作物相比，减少翻耕覆盖作物在秋季最大限度地减少了 N2 O 排放峰值。然而，相对于耕作的覆盖作物，尽管土壤无机 N 减少，但减少耕作的覆盖作物并未减少潜在的可浸出的 NO3。覆盖作物 N 同位素表明，三叶草 N 可能在冬季矿化和浸出。我们的结果表明，减耕覆盖作物可以减少 N2 O 排放，以减轻农业对气候的影响，但应选择冬季耐寒的覆盖作物来减轻浸出。本文受版权保护。版权所有。