Cover Crops: Nitrogen, Weeds, Insects, Disease, Soil Quality, and Economics.

Cover crops have been used in Ontario vegetable production for decades, but there is limited knowledge of the interactions of multiple factors such as yield, N cycling, pest dynamics, soil quality and economics in the subsequent crop. To improve better management practices, a study at two locations was conducted to characterize the effect of winter cover crops on the subsequent sweet corn (Zea mays L.) crop. The cover crop treatments included a no cover crop control, oat (Avena sativa L.), cereal rye (Secale cereale L.), oilseed radish (OSR) (Raphanus sativus L. var. oleiferus Metzg Stokes), and oilseed radish with rye. Sweet corn total yield was unaffected by prior cover crop treatment. By sweet corn harvest, there was no difference in plant available N among cover crop treatments at either site.  Previous cover crops did not affect weed biomass and or density, provided that OSR does not set viable seed. There was no difference in wireworm populations between prior cover crop treatments, but in both years there was higher European corn borer pressure in sweet corn following cereal cover crops compared to the other treatments. Rust, corn earworm, smut, and Northern leaf blight were either not observed or trends were inconsistent between years.  Other than bait lamina tests, cover crop treatments had no effect on soil quality parameters (soil shake ratings, bulk density, spring temperature and moisture).  Bait lamina is an indirect measurement of biological activity, and was highest in the oat cover crop at both sites.  Although there was no statistical difference in sweet corn yield, economic analysis indicated that, at both sites, cover crops were as profitable as or more profitable than the no cover crop control. Thus, the cover crops tested are practical and profitable options to include in sweet corn production systems.