Legume cover crops can play a valuable role in maintaining and increasing soil quality and nitrogen availability, but are infrequently grown in the Upper Midwest due to short growing seasons with minimal management windows; cold, wet springs; and harsh winters. This study was performed to assess the viability of winter annual legume species in northern climates as a potential source of nitrogen (N) fertility to a 75-day sweet corn (Zea mays convar. saccharata var. rugosa) cash crop in Lamberton and Grand Rapids, MN in 2016 and 2017. Treatments included medium red clover (Trifolium pratense), two cold-hardy ecotypes of hairy vetch (Vicia villosa Roth), a cereal rye-hairy vetch biculture (Secale cereale L., Vicia villosa Roth), cereal rye as a non-legume control, and a fallow weed-free control. Legumes were split into rhizobia inoculated and non-inoculated treatments. Inoculation had no effect on nodulation, biomass production, or N fixation likely due to competition with endogenous rhizobia strains. The rye monoculture and biculture produced the most biomass at all site-years averaging 7.7 and 7.0 Mg ha⁻¹ respectively while the two vetch ecotypes averaged 4.5 and 3.9 Mg ha⁻¹. Both vetch ecotypes contributed among the most nitrogen in all site-years, contributing up to 211 kg N ha⁻¹ from aboveground biomass. Data from natural abundance isotopic approaches indicate that 75% of vetch tissue N in Grand Rapids and 59% of vetch tissue N in Lamberton was derived from atmospheric N fixation, with equal or higher percent fixation of vetch in biculture at all site-years. More studies should be performed to better understand controls on N fixation of legume cover crops in cold climates.

中文翻译：

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中西部上部有机种植系统中冬季一年生豆科植物的固氮和生产力

豆科农作物在维持和提高土壤质量和氮素利用率方面可以发挥重要作用，但由于生长期短，管理窗口少，因此在中西部上层不常种植。寒冷潮湿的泉水；和严酷的冬天。进行这项研究，以（N）的生育评估北方气候的冬季年度豆类品种的可行性氮的潜在来源，到75天的甜玉米（玉米convar：S accharata变种藿香）经济作物在兰伯顿和大明尼苏达州的拉皮兹（Rapids）在2016年和2017年。处理措施包括中等红三叶草（Trifolium pratense），两种耐寒生态型的毛etch子（Vicia villosa Roth），谷类黑麦-毛v子双养（Secale谷物L.，野豌豆（Vicia villosa Roth），谷物黑麦作为非豆类对照，以及无休闲杂草对照。豆科植物分为接种根瘤菌和不接种根瘤菌的治疗方法。接种对结瘤，生物量生产或固氮均无影响，这可能是由于与内源根瘤菌菌株竞争造成的。黑麦单作和双作在所有产地年均产生最多的生物量，平均分别为7.7 Mg ha ^-1和7.0 Mg ha ^-1，而两个紫etch生态型平均为4.5 Mg ha ^-1和3.9 Mg ha ^-1。两种紫云英生态型在所有立地年中贡献最大的氮素，贡献高达211 kg N ha ^-1来自地上的生物质。来自自然丰度同位素方法的数据表明，大急流城中75％的etch子组织N和Lamberton中59％的N子组织N来源于大气固氮，在所有立地年中，双文化中ation子的固着率均相等或更高。应该进行更多的研究，以更好地了解寒冷气候下对豆科植物的固氮控制。