Harvest Management Effects on Alfalfa Yield and Root Carbohydrates in Three Georgia Environments

Abstract

AbstractAlfalfa (Medicago sativa L.) hay harvest management may need to be modified in the southeastern USA due to the mild winters and hotter summers compared with northern production areas. The objectives of this study were to evaluate the effect of three harvest treatments (10, 50, and 10% bloom until midsummer when one harvest was delayed until 50% bloom‐referred to as “summer rest” management) on herbage yield and seasonal trends of total nonstructural carbohydrates (TNC) in the roots of irrigated semidormant ‘Apollo’ and nondormant ‘Fla‐77’ alfalfa. The experiments were conducted for 2 yr in the Georgia Mountains on Bradson clay loam (Typic Hapludult, clayey, oxidic, mesic), Piedmont on Cecil sandy clay loam (Typic Hapludult, clayey, thermic, kaolinitic), and Coastal Plain on Greenville sandy clay loam (Rhodic Paleudult, clayey, thermic, kaolinitic). Alfalfa at all three locations gave satisfactory yield (12.7 Mg ha−1) when harvested at 10% bloom throughout the growing season including late fall. There was no advantage to either cultivar from harvesting at 50% bloom or allowing a summer rest period. Location effects were minimal. Root TNC concentrations were lowest in midsummer, greatest in late autumn, and decreased during winter. Root TNCs ranged from 200 to 560 g kg−1 for Fla‐77 and 150 to 580 g kg−1 for Apollo. There was no effect of cultivar or harvest management on root TNC concentrations. These results indicate that root TNCs are not a primary limiting factor for alfalfa hay production in the southeastern USA and that harvest can continue throughout the year with no adverse effect on forage yield.