Legume Cover Crop Options for Grain Rotations in Wisconsin

Use of forage legumes as cover crops in the year prior to corn (Zea mays L.) is one way to reduce the amount of N fertilizer used in corn production. This study evaluated several forage legumes for dry matter (DM) production during the seeding year when established in grain rotations. Field studies were conducted near Arlington and Marshfield, WI, in 1989 and 1990. Treatments consisted of nine forage legumes: medium and mammoth red clover (Trifolium pratense L.), dormant and nondormant alfalfa (Medicago sativa L.), alsike clover (T. hybridum L.), ladino clover (T. repens L.), hairy vetch (Vicia villosa Roth), and two cultivars of yellow sweetclover [Melilotus officinalis (L.) Lam.]. Five establishment treatments tested were: seeded in the spring, companion-seeded with oat (Avena sativa L.), interseeded into corn at last cultivation, and seeded following harvest of either canning pea (Pisum sativum L.), or oat for grain. In general, legume DM yields were highest in establishment periods which offered the longest growing season with the least amount of competition from the primary crop. Hairy vetch, the only annual legume used in the study, produced the highest yields in each of the five establishment periods, as high as 9.76 Mg ha⁻¹ when spring seeded. The climbiing nature of this legume, however, makes it an unwise choice for companion seeding with small grains, a situation where the true clover species are best adapted. Dry soil conditions following pea or oat harvest often limited legume germination, seedling growth, and ultimately DM yield. Interseeding of legume cover crops into corn at last cultivation resulted in low seeding-year DM yields. From the results of this study, we conclude that several legume-establishment period combinations could be used successfully to produce N-containing biomass.