Establishment and Impact of Cover Crops Intersown into Corn

In temperate climates, corn (Zea mays L.) is often harvested too late for sufficient cover crop growth to meet grower objectives. This study was conducted to evaluate intersowing into standing corn in terms of cover crop establishment and growth and the impact on corn yield. Three experiments were conducted from 2009 to 2011 in southwestern Ontario sweet and hybrid seed corn production systems to assess timing of cover crop intersowing, utility of alfalfa (Medicago sativa L.) and 17 other cover crops species or multispecies mixes. In all 22 locations over 3 yr, corn yield was not affected in any of the three cover crop experiments. Sweet corn cover crop treatments exhibited poor stands of limited growth (< 1% ground coverage) at corn harvest, attributed to sweet corn canopy closure. At seed corn harvest, early-sown (corn V4-V6) cover crops accumulated 1116 kg ha(-1) dry biomass and 42.4 kg N ha(-1), which were 33% greater than the late-sown (V10-V12) treatments. A lack of a cover crop effect compared with the no-cover-crop treatment in soil mineral N and corn yield indicates little N competition. Hairy vetch (Vicia villosa Roth), oilseed radish (OSR, Raphanus sativus L. var. oleoferus Stokes) and three of six cover crop blends were the only treatments to accumulate dry biomass over 1000 kg ha(-1) by corn harvest. Of the cover crops evaluated, interseeding into hybrid seed corn production systems appears to be of little risk to yield and can provide ground cover during postharvest fallow periods.