Shifting from reduced tillage (RT) to no-till (NT) often reduces phosphorus (P) runoff by minimizing soil erosion. However, it might increase nitrous oxide (N2O) emissions or nitrate-N (NO3-N) leaching. Including a legume cover crop such as hairy vetch (Vicia villosa L.) before corn (Zea mays L.) is a common practice among growers in the Midwest USA. However, the effects of hairy vetch following soybean (Glycine max L.) harvest on NO3-N leaching and N2O emissions during the following corn season in soil with clay and fragipans are less assessed. This study evaluated the influence of cover crop (hairy vetch vs. no-CC control) and tillage systems (NT vs. RT) when 179 kg ha−1 nitrogen (N) was applied at planting on (i) corn yield, N uptake, removal, and balance; (ii) N2O emissions and NO3-N leaching; (iii) yield-scaled N2O emissions and NO3-N leaching during two corn growing seasons. We also evaluated factors influencing N2O emissions and NO3-N leaching via principal component analysis. Corn grain yield was higher in RT (8.4 Mg ha−1) than NT (6.2 Mg ha−1), reflectingmore available N in the soil in RT than NT, possibly due to the favorable aeration and increased soil temperature in deeper soil layers resulting from tillage. Hairy vetch increased corn grain yield and soil N. However, it led to higher losses of both N2O-N and NO3-N, indicating that increased corn grain yield, due to the hairy vetch’s N contribution, also resulted in higher N losses. Yield-scaled N2O-N emissions in NT-2019 (3696.4 g N2O-N Mg−1) were twofold higher than RT-2019 (1872.7 g N2O-N Mg−1) and almost fourfold higher than NT-2021 and RT-2021 indicating in a wet year like 2019, yield-scaled N2O-N emissions were higher in NT than RT. Principal component analysis indicated that NO3-N leaching was most correlated with soil N availability and corn grain yield (both positive correlations). In contrast, due to the continued presence of soil N, soil N2O-N fluxes were more driven by soil volumetric water content (VWC) with a positive correlation. We conclude that in soils with claypan and fragipans in humid climates, NT is not an effective strategy to decrease N2O-N fluxes. Hairy vetch benefits corn grain yield and supplements N but increases N loss through NO3-N leaching and N2O-N emissions.

中文翻译：

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毛茸茸薇对减耕和免耕系统中玉米生长季节一氧化二氮和硝酸盐浸出损失的影响


从少耕 （RT） 转向免耕 （NT） 通常可以通过最大限度地减少土壤侵蚀来减少磷 （P） 径流。但是，它可能会增加一氧化二氮 （N2O） 排放或硝酸盐 N （NO3-N） 浸出。在美国中西部种植者中，先加入豆科覆盖作物，如毛茸茸 （Vicia villosa L.），然后再种植玉米 （Zea mays L.）。然而，大豆 （Glycine max L.） 收获后毛茸茸对下一个玉米季节在有粘土和薄片的土壤中 NO3-N 浸出和 N2O 排放的影响评估较少。本研究评估了在种植时施用 179 kg ha-1 氮 （N） 时覆盖作物（大紫云英与无 CC 对照）和耕作系统（NT 与 RT）对 （i） 玉米产量、氮吸收、去除和平衡的影响;（ii） N2O 排放和 NO3-N 浸出;（iii） 两个玉米生长季节的产量规模 N2O 排放和 NO3-N 浸出。我们还通过主成分分析评估了影响 N2O 排放和 NO3-N 浸出的因素。RT （8.4 Mg ha-1） 的玉米籽粒产量高于 NT （6.2 Mg ha-1），反映 RT 土壤中的有效氮比 NT 多，这可能是由于耕作导致较深土壤层的良好通气和土壤温度升高。毛茸茸增加了玉米籽粒产量和土壤氮。然而，它导致 N2O-N 和 NO3-N 的损失更高，表明由于毛豌紫云英的 N 贡献，玉米籽粒产量的增加也导致了更高的 N 损失。NT-2019 的产量比例 N2O-N 排放量 （3696.4 g N2O-N Mg-1） 比 RT-2019 高两倍 （1872.7 g N2O-N Mg-1），比 NT-2021 和 RT-2021 高近四倍，表明在像 2019 年这样的丰水年，NT 的产量比例 N2O-N 排放量高于 RT。 主成分分析表明，NO3-N 淋溶与土壤氮有效性和玉米籽粒产量最相关 （均为正相关）。相比之下，由于土壤 N 的持续存在，土壤 N2O-N 通量更多地受土壤体积含水量 （VWC） 的驱动，呈正相关。我们得出的结论是，在潮湿气候下具有粘土板和 fragipans 的土壤中，NT 不是减少 N2O-N 通量的有效策略。毛茸茸有利于玉米籽粒产量并补充氮，但会通过 NO3-N 浸出和 N2O-N 排放增加氮损失。