Defoliation management affects performance of alfalfa–bermudagrass mixtures in the southeastern United States

Abstract

AbstractOverseeding alfalfa (Medicago sativa L.) into grass swards increases forage nutritive value and reduces N fertilizer requirement. In warm climates, establishing and maintaining alfalfa in mixtures with vigorous C4 grasses is challenging, which makes adjustment of defoliation management critical. The objective of this 2‐year study was to determine optimal harvest stubble height (SH; 5, 10, and 15 cm) and cutting interval (CI; 2, 4, and 6 weeks) for two alfalfa genotypes (“Bulldog 805,” and breeding line UF Alf Pers 2015 [UF 2015‐AP]) in mixture with “Tifton 85” bermudagrass (Cynodon spp.). When statistical differences occurred, shorter SH resulted in greater mixture forage accumulation (FA), with this effect generally more pronounced for UF 2015‐AP than Bulldog 805, and for CI of 6 weeks than 2 or 4 weeks. Genotype did not affect alfalfa FA, but alfalfa FA was least for the 2‐week CI for all SH levels, and greatest for the 5‐cm SH when CI was 4 weeks, and for the 5‐ and 10‐cm SH when CI was 6 weeks. Alfalfa percent cover was generally greater for longer CI, regardless of SH. Mixture crude protein and digestibility were minimally affected by treatments because the expected negative effects of long CI on nutritive value were offset by greater alfalfa proportion in the mixture for these treatments. In this environment, CI was generally the most important factor affecting alfalfa persistence in alfalfa–bermudagrass mixtures. A short SH in combination with longer CI (4–6 weeks) resulted in the greatest mixture and alfalfa FA.