Row Spacing and Nitrogen: Effect on Alfalfa‐Bermudagrass Yield and Botanical Composition

Abstract

AbstractInterseeding perennial legumes into bermudagrass [Cynodon dactylon (L.) Pers.] sods should increase forage quality. Preliminary research revealed 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 maintenance and bloat prevention. It may be possible to manipulate botanical composition with N and row spacing. The objective of this research was to examine effects of these factors on botanical composition and yield of alfalfa‐BG swards. We interseeded alfalfa into ‘Tifton 44’ BG in 20‐, 40‐, and 60‐cm row spacings, and included a non‐interseeded check treatment. Experiments were on Norfolk sandy loam (fine‐loamy, siliceous, thermic Typic Kandiudult) and Cecil sandy clay loam (clayey, kaolinitic, thermic Typic Kanhapludult) sites. Nitrogen was applied at 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 total yields over BG alone, at all but the highest rates of N. Nitrogen increased yields of interseeded plots an average of 11%. Yield increases 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 effect or decreased grass percentage, whereas wide row spacing usually increased the grass component. It appears that alfalfa utilized a significant portion of applied N, and that N will not aid in retaining BG in mixtures. Increasing row spacing will aid in retaining grass in mixture, probably through reduced shading of grass.