Integration of cover crops into no-till and ridge-till wheat (Triticum aestivum L.) – corn (Zea mays L.) cropping sequence

Abstract

The use of underseeded red clover (Trifolium pratense L.) as a cover crop in winter wheat has been declining because of poor clover establishment during dry growing seasons, the lack of selective herbicides for weed control in clover, and the difficulty in using burn-down herbicides to remove the clover before planting no-till corn. During 1990–1992, we conducted on-farm trials on silt loam no-till and sandy ridge-till fields in southern Ontario to evaluate the establishment and growth of alternative stubble-seeded cover crops following wheat and their effects on subsequent weed and volunteer wheat growth. In general, oats (Avena sativa L.), oilseed radish (Raphanus sativus L.), and barley (Hordeum vulgare L.) produced more biomass than the other stubble-seeded cover crops, hairy vetch (Vicia villosa Roth.), red clover, and buckwheat (Fagopyrum esculentum L.). In comparison, winter-hardy underseeded hairy vetch and red clover produced the most biomass and provided better weed control; however, any reduction in herbicide use is offset by the need to burn down these cover crops. An evaluation of cover-crop effects on post-wheat-harvest weed growth was not possible because of sparse and variable weed growth, which occurred even in the absence of a cover crop. However, volunteer wheat biomass was inversely correlated with cover-crop biomass. At the no-till site, cover-crop response to straw baling and the subsequent effects on weed and volunteer wheat growth and corn performance also were evaluated. Straw baling had minimal effects on cover-crop growth; however, volunteer wheat growth doubled. No-till corn was not adversely affected by the amounts of residue present where cover crops were established the previous year. Importantly, reducing the amount of wheat straw by baling increased early-season growth rates and corn grain yield by 0.91 Mg ha−1. We conclude that alternative stubble-seeded cover crops, such as oats, barley and oilseed radish, are suitable for no-till corn. At present, cover crops augment weed management but are not a substitute for herbicides, as burn-down herbicides are required to remove existing weeds or winter-hardy cover crops. Key words: Underseeded, stubble seeded, baling, volunteer wheat