Cover Crop Nitrogen Cycling in a Sweet Corn Rotation.

Limited knowledge currently exists on cover crop N dynamics in vegetable rotations in southern Ontario. Therefore, to improve N best management practices, a study was conducted to characterize the effect of winter cover crops on N cycling prior to sweet corn (Zea mays L.), at two locations. The main plot factor was cover crop type and the split-plot factor was N fertilization (0 and 140 kg N ha^-1 preplant broadcast incorporated) of the sweet corn 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 (OSR+rye). Over the fall and winter, cover crops resulted in higher plant available N (PAN) than the no cover control at Site 1, but not at Site 2. Despite this, cover crops at both sites had higher total N budgets (output - input of soil and plant N) over the entire cover crop growing season than the control, indicating that the cover crops likely prevented N losses during an otherwise fallow period. However, by sweet corn harvest, there was no difference in PAN between any of the treatments at either site. Sweet corn marketable yield was unaffected by the cover crops. This suggests that N fertilizer rates do not have be adjusted when cover crops precede sweet corn, compared to when no cover crop is included in the rotation. Although there was no statistical difference in sweet corn yield, economic analyses 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 feasible options to include in sweet corn production.