Tillage and cropping systems - No-tillage corn and grain sorghum response to cover crop and nitrogen fertilization

No-tillage cropping systems may benefit from the addition of winter annual cover crops through decreased soil erosion, accumulation of biologically fixed N, or increased crop yield. The objectives of this research were to assess the amount of cover provided by winter annual legumes and oat (Avena sativa L.) to quantify the fertilizer N equivalent value of each cover crop system and the effect of cover crop and N rate on corn (Zea mays L.) and grain sorghum [Sorghum bicolor (L.) Moench] grain yield. Two experiments, one in corn and one in sorghum, were conducted in 1997,1998, and 1999. In each experiment, the main-plot effect was cover crop treatment while the subplot effect was spring N rates of 0, 56, 112, and 168 kg ha(-1). The addition of oat to the legume cover crop treatments increased fall ground cover but decreased total spring dry matter yield. Maximum spring dry matter yield was greatest in the hairy vetch (Vicia villosa Roth)-alone treatment. Hairy vetch alone also produced the greatest mean fertilizer N equivalent value in the corn and sorghum experiments, 43.6 and 56.9 kg N ha(-1), respectfully. These values, however, were variable among years. Corn and sorghum grain yield were greatest in the Austrian winter pea (Pisum sativum L.) and hairy vetch full seeding rate treatments, 5.19 and 7.06 Mg ha(-1), respectfully. Our results indicate that winter annual cover crops provide several distinct benefits to no-tillage corn and sorghum production systems and that cover crops should be selected based on specific grower needs.