EFFECTS OF TILLAGE AND WINTER COVER CROPS ON NITROGEN REQUIREMENTS OF CORN IN INDIANA (AUSTRIAN WINTER PEA, HAIRY VETCH)
Abstract
Field experiments were conducted at two locations in Indiana, from 1982 through 1985, in order to evaluate the use of winter annual cover crops in corn production. The cover crop species were hairy vetch (Vicia villosa Roth), Austrian winter pea Pisum sativum spp. arvense (L.) Poir , and wheat (Triticum aestivum L.). Two seeding dates/methods were employed with each: early September/overseeded into standing corn, and October/drilled into corn stubble. Cover crops were sampled in mid-May, prior to planting corn, in order to estimate dry matter yields and to determine nitrogen content of aboveground plant tissues. Corn was planted into herbicide-killed covers as well as in no-till (NT) plots covered only by corn residue and in others which had been plowed in the spring (conventional tillage, CT). Nitrogen fertilizer (0, 45, 90, 135, 180 kg N ha('-1)) was applied, as anhydrous ammonia, to subplots within each tillage/cover crop whole-plot. Growth of the covers varied significantly with location and with year, reflecting annual differences in temperature and precipitation during winter and early spring. Results from the northern location (Wanatah, IN) indicated that spring regrowth would not provide adequate cover during the period prior to corn planting. At the south-central location (Bedford, IN), hairy vetch performed more consistently and seemed more resistant to winter-kill that did the other legume, Austrian winter pea. Only in 1985 did dry matter yields of all cover crops exceed 2000 kg ha('-1), with complete soil surface cover achieved by mid-March. Vetch dry matter yields were higher with overseeding; pea dry matter yields were higher with drilling. During the three years of this study, corn grain yields reflected little response to the higher rates of N fertilization. At Bedford, three-year averages of corn yields, averaged over N treatments, conformed to the following pattern with respect to tillage/cover crop treatment; NT/vetch > NT/pea > NT/wheat > NT/cover > CT. It should be noted that this period included a drought year, 1983, during which all NT treatments produced higher yields than the CT treatment. Estimates of nitrogen contributed by the legumes to the succeeding corn crop averaged 45 kg ha('-1) for pea and 64 kg ha('-1) for vetch.
Degree
Ph.D.
Subject Area
Agronomy
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