Optimizing Hairy Vetch Management in Strip-Tilled Sweet Corn

The use of leguminous hairy vetch (Vicia villosa) as a cover crop in combination with reduced tillage can reduce the economic and environmental costs associated with the use of fossil fuels in food production. Additional economic and environmental benefits may be realized when hairy vetch is grown in combination with winter rye (Secale cereale). However, use of hairy vetch is hindered by high seed costs, risks associated with winter-kill in Northern climates, and re-growth, especially in reduced tillage systems. New varieties of early-flowering, winter-hardy hairy vetch (“Purple Prosperity” and “Purple Bounty”) may overcome these obstacles, but little is known about their performance in mixtures, or their effects on subsequent crops. This research was conducted to evaluate early-flowering hairy vetch varieties for re-growth following mowing, assess vetch variety compatibility with winter rye, and estimate the impact of vetch monocultures and rye-vetch mixtures on nitrogen dynamics and yield of strip-tilled sweet corn. Cover crop treatments were bare ground, winter rye (“Wheeler”) alone, and three varieties of hairy vetch (Purple Prosperity and Purple Bounty with “Oregon” vetch as a control) grown alone and in mixture with rye. Initial nitrogen application rates were reduced in cover crop treatments using N credits (25 lbs for rye, 75 lbs for vetch and 75 lbs for rye-vetch) based on cover crop biomass. No remarkable re-growth was observed for any of the vetch varieties despite significantly earlier flowering in the new varieties. New vetch varieties had equivalent overwinter survival and overall biomass production compared to Oregon vetch when grown alone or in mixture with winter rye. Initial soil nitrate levels in bare ground and vetch-only plots were approximately twice that of rye and rye-vetch plots. Rapid early declines in nitrate levels in these treatments suggest that much of this initial nitrate was irrecoverably lost. Slower mineralization in rye and rye-vetch treatments suggests better synchrony with sweet corn demand early in the season. However, lower nitrate levels in these treatments late in the season suggest that higher rates of side-dressing may have been desirable to insure against possible yield losses. Despite reduced initial application rates of nitrogen in cover crop plots, there were no significant differences in sweet corn yield between the bare ground, rye only, vetch only and rye-vetch plots. These results suggest that the early-flowering vetch varieties are suited for use in northern climates and can adequately supply the early season nitrogen demands of strip-tilled sweet corn.