ROW SPACING AND NITROGEN - EFFECT ON ALFALFA BERMUDAGRASS YIELD AND BOTANICAL COMPOSITION

Interseeding perennial legumes into bermudagrass [Cynodon dactylon (L. ) Pers.] sods should increase forage quality. Preliminary research rev ealed that alfalfa (Medicago sativa L.) interseeded into bermudagrass (BG) rapidly reduced BG vigor, possibly because of shading by alfalfa. Grass-legume pastures should contain balanced mixtures for quality ma intenance and bloat prevention. It may be possible to manipulate botan ical composition with N and row spacing. The objective of this researc h was to examine effects of these factors on botanical composition and yield of alfalfa-BG swards. We interseeded alfalfa into 'Tifton 44' B G in 20-, 40-, and 60-cm row spacings, and included a non-interseeded check treatment. Experiments were on Norfolk sandy loam (fine-loamy, s iliceous, thermic Typic Kandiudult) and Cecil sandy clay loam (clayey, kaolinitic, thermic Typic Kanhapludult) sites. Nitrogen was applied a t 0, 112, 224, and 448 kg ha-1 yr-1. Yield of BG increased by a factor of 2.06 with 448 kg ha-1 of N, compared with 0 N. Alfalfa increased t otal yields over BG alone, at all but the highest rates of N. Nitrogen increased yields of interseeded plots an average of 11%. Yield increa ses from N did not result from increased grass percentage. Increasing row spacing decreased yields of interseeded mixtures, but increasing N rate sometimes compensated slightly for wide rows. Nitrogen had no ef fect or decreased grass percentage, whereas wide row spacing usually i ncreased the grass component. It appears that alfalfa utilized a signi ficant portion of applied N, and that N will not aid in retaining BG i n mixtures. Increasing row spacing will aid in retaining grass in mixt ure, probably through reduced shading of grass.