Fitting Winter Annual Legumes into a Corn/Soybean Rotation.

Crimson clover  (Trifolium incarnatum L.) and hairy vetch (Vicia villosa Roth) cover crops are being re-evaluated in North Carolina as potentially cost effective N fertilizers for a following corn (Zea mays L.) crop.  Past studies have documented 100+ kg N/ha productivity levels, but these were usually in crop rotations (tobacco/corn, continuous corn) which allowed cover crop planting during the optimum mid-September/early October window.  Planting dates within this window may require aerial overseeding into soybean (Glycine max L. Merrill).  Results from a moderately well-drained coastal plain site and poorly drained tidewater sites suggest that crimson clover may produce >80 kg N/ha on well drained soils, but usually <50 kg N/ha on poorly drained soils.  Hairy vetch was only evaluated on poorly drained soils, and may produce >100 kg N/ha.  Overseeding prior to soybean leaf drop resulted in better stands than did overseeding at last soybean cultivation (August), and was usually better than drilling after soybean harvest (October/November).  Corn grain yields and the apparent N contribution to the corn crop will be presented.