INTERSEEDED FORAGE LEGUME POTENTIAL AS WINTER GROUND COVER, NITROGEN-SOURCE, AND COMPETITOR

Legume winter ground covers may contribute to row crop systems by providing protection from wind and precipitation and by releasing N to the subsequent row crop, but to attain effective size, these legumes must begin growth well before the winter. A 3-yr study was conducted to evaluate the performance of four commonly used forage legumes interseeded into corn (Zea mays L.). Alfalfa (Medicago sativa L.), yellow sweetclover (Melilotus officinalis Lam.), red clover (Trifolium pratense L.), and alsike clover (T. hybridum L.) were seeded in a mix consisting of equal seed numbers (pure live seed) from each species. Seeding dates were (i) at corn planting and (ii) at last cultivation. Control treatments were nonseeded. Two levels of weed control also were evaluated. In addition to the factorial experiment, the four species were seeded separately in other corn plots. The herbicide EPTC was also evaluated for use in interseeding. In drier than normal seasons (summer of 1984 and spring of 1985), soil moisture was significantly depleted under interseedings; this depletion was not observed in seasons of normal precipitation. Legume stands and ground cover reflected moisture and light conditions during establishment. In the 2 yr that rows were oriented east-and-west, stands conformed to a skewed modal distribution across the inter-row. Alfalfa and sweetclover usually were better established and produced more cover than either red or alsike clover. Corn yields were not significantly reduced by interseeding per se, but they were reduced when interseeding at the early date interrupted weed control. In treatments that used the herbicide, corn yields were greater than where herbicide was not used, but yields were still significantly below those of the nonseeded control.