The Interaction of Annual Ryegrass and Nitrogen on Arrowleaf Clover in the Southeastern United States

Nitrogen enhances annual ryegrass (Lolium multiflorum Lam.) growth on the infertile Coastal Plain soils in the southeastern United States but N can be antagonistic to clovers. Nitrogen rate and time of application were evaluated on an arrowleaf clover (Trifolium vesiculosum Savi.)-annual ryegrass mixture growing on a Coastal Plain soil for 3 yr in northeast Texas. Fertilizer treatments were 0, 34, 67, or 101 kg N ha(-1) at planting or first true clover leaf (FCL) stage followed by 0 or 67 kg N ha(-1) in December and March. Planting, FCL, and December N applications enhanced ryegrass production but had little effect on arrowleaf clover production by mid March. The general trend was for clover percentage and yield to decrease and ryegrass yield to increase as the total amount of N fertilizer applied increased. The no-N treatment always had the greatest percentage clover usually followed by single N application treatments with clover percentages greater than 50%. Average annual yield of ryegrass alone without N was 1139 kg ha(-1) compared to 4038 kg ha(-1) with 201 kg N ha(-1). Applying 67 kg N ha(-1) at FCL and in December and March was always one of the most productive N treatments. Applying 67 kg N ha(-1) only twice at FCL and in December was the best compromise for maintaining a high clover percentage and clover-ryegrass yield and was always equal to ryegrass alone with three applications of 67 kg N ha(-1).