Morphological development of alfalfa cultivars selected for higher quality

Alfalfa (Medicago sativa L.) maturity at the time of harvest greatly influences forage quality. The objective of this research was to determine if observed quality differences between high quality and other alfalfa cultivars were due to differences in morphological development. Two high-quality cultivars ('WL 252HQ', 'WL 322HQ') and two check cultivars ('5262', '5454') with similar fall dormancy ratings were established on a Murrill silt loam (fine-loamy, mixed, mesic Typic Hapludult) in the spring of 1996. During 1997, 1998, and 1999, each cultivar was hand-sampled weekly for 4 consecutive wk during the spring growth period and for 3 consecutive wk during the three subsequent growth periods. Morphological development and forage quality were determined for each alfalfa cultivar at each sampling. There were no interactions between growth period or sampling times and alfalfa cultivars for either alfalfa maturity or forage quality. Morphological development of the cultivars was not different at any of the sampling times. Averaged across all growth periods and sampling times, crude protein (CP) concentrations and in vitro dry matter digestibility (IVDMD) were 14 and 13 g kg^-1, respectively, higher for the high-quality cultivars (ADF) and neutral-detergent fiber (NDF) concentrations were 16 and 15 g kg^-1, respectively, lower. The data from this research indicates that the difference in quality between the high quality and traditional alfalfa cultivars is not due to differences in morphological development. Selecting for higher-quality alfalfa was successful and is not an artifact of inadvertently selecting for delayed development.