Harvest Management Impacts On Stem Quality in Alfalfa.

The concentration of stem cell wall constituents in alfalfa, Medicago sativa L., herbage can affect dry matter intake and energy availability in dairy and beef production systems, and impact energy conversion efficiency when alfalfa is used to produce biofuels. Stem total cell wall concentration, Klason lignin, and polysaccharide composition are affected by harvest maturity and environmental influences. Knowledge of the environmental influence and variability of the stem cell wall concentration and component traits would be essential in a plant breeding program with goals to improve forage quality and biofuel conversion efficiency. We evaluated total stem cell wall concentration (g kg^-1 dry matter), Klason lignin, glucose, xylose, mannose, fucose, uronic acids, arabinose, galactose, and rhamnose (g kg^-1 cell wall) in six alfalfa germplasms established at two plant densities (180 and 450 plants m²) at two locations (Arlington, WI and Becker, MN) and harvested at two maturity stages, early bud (4 cuts per season), and full flower (3 cuts per season) for two years. Stem cell wall concentration and composition traits responded differently at MN and WI and between the two years. Plant density had no effect on stem cell wall concentration or composition at either location.  Cell wall compositional changes between the two maturity stages differed between MN and WI. At MN the plants gained a greater proportion of glucose compared to Klason lignin, at the later maturity stage, while the opposite was true at WI. The other stem cell wall polysaccharides showed inconsistent responses among the germplasms evaluated at the locations.