Interseeding alfalfa (Medicago sativa L.) into silage corn (Zea mays L.) can improve forage yield, farm profitability, and soil conservation, but unreliable alfalfa establishment hampers on-farm adoption. This study evaluated seedling survival and growth of 36 alfalfa varieties differing in reported plant traits when interseeded at two Wisconsin sites in 2015 and at single sites in Wisconsin, Michigan, and Pennsylvania in 2016. Subplots of alfalfa varieties were sprayed with prohexadione-calcium (PHD) at 0 or 0.42 kg acid equivalent (a.e.) ha^–1 to assess changes in seedling survival mediated by this growth retardant. After corn harvest in 2015, average stand density of varieties in Wisconsin ranged from 15 to 94 plants m^–2 without PHD and from 52 to 199 plants m^–2 with PHD. Stand density largely determined subsequent first-cut alfalfa dry matter yield, which ranged from 1.1 to 6.3 Mg ha^–1. After corn harvest in 2016, stand density of varieties averaged across PHD treatments ranged from 113 to 248 plants m^–2 in Michigan and Pennsylvania, compared with only 0.5 to 26 plants m^–2 in Wisconsin; PHD treatment improved stand density only in Wisconsin but could not ensure adequate establishment under wet conditions that favored vigorous corn growth and foliar disease on alfalfa. Overall, establishment was poorly related to measured or reported alfalfa traits, but ‘55H94’ and hybrids were consistently among the best performing cultivars. Further work is needed to understand seedling survival mechanisms and to develop improved germplasm and production practices to ensure reliable establishment of interseeded alfalfa.

中文翻译：

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玉米青贮饲料间种苜蓿品种的差异成活

将苜蓿 ( Medicago sativa L.)播种到青贮玉米 ( Zea mays L.) 中可以提高牧草产量、农场盈利能力和土壤保持，但不可靠的苜蓿种植会阻碍农场采用。本研究评估了 2015 年在威斯康星州的两个地点和 2016 年在威斯康星州、密歇根州和宾夕法尼亚州的单个地点间播种时报告的植物性状不同的 36 个苜蓿品种的幼苗存活和生长。 ) 0 或 0.42 kg 酸当量 (ae) ha ^–1以评估由该生长抑制剂介导的幼苗存活率变化。2015 年玉米收获后，威斯康星州品种的平均林分密度为 15 至 94 株 m ^–2没有博士和从 52 到 199 株植物 m ^–2有博士。林分密度在很大程度上决定了随后第一次切割的苜蓿干物质产量，其范围为 1.1 至 6.3 Mg ha ^–1。2016 年玉米收获后，在密歇根州和宾夕法尼亚州，PHD 处理的平均林分密度范围为 113 至 248 株 m ^–2，而只有 0.5 至 26 株 m ^–2在威斯康星州；PHD 处理仅在威斯康星州提高了林分密度，但不能确保在有利于玉米旺盛生长和苜蓿叶病害的潮湿条件下充分建立。总体而言，建立与测量或报告的苜蓿性状的相关性较差，但“55H94”和杂交种一直是表现最好的品种。需要进一步的工作来了解幼苗存活机制并开发改良的种质和生产实践，以确保可靠地建立间种苜蓿。