Cutting Strategy Effects on Forage Mass Accumulation of Four Warm-Season Grass Species.

Warm-season grasses can be used to increase forage yield, extend the grazing season, and utilize soils of poor fertility in the Southern United States. Sward height is commonly used to determine the appropriate time for cutting or grazing warm and cool-season forage grasses based on plant maturity and accumulated herbage mass at designated heights. Rapid regrowth rates of these grasses during mid-summer can be beneficial for producers who need additional forage when cool-season grass growth is reduced. The objective of this experiment was to estimate forage mass accumulation of four warm-season grasses (bermudagrass, crabgrass, switchgrass and sorghum-sudangrass) throughout the summer in Tennessee under different cutting strategies. The experiment was conducted during the 2013-2015 growing seasons at the University of Tennessee Plateau AgResearch and Education Center in Crossville, TN. Height-based cutting regimes, were imposed on each species. Plots were measured weekly for average sward height and a cut was implemented each time the sward reached its target height, being 76-cm down to 20-cm for switchgrass and sorghum-sudangrass, while bermudagrass and crabgrass were cut when reaching 30-cm down to 8-cm. Forage mass was fitted to time (t, an independent variable) using the Gompertz equations with PROC NLIN of SAS to best fit the data. Height-based cuttings had similar forage mass accumulation among height periods. Most height-based cuttings in all species were unfeasible to test due to a very high accumulation rate in the beginning of the growing season. Height-based multiple cuttings can recommended for all species in this experiment. However, often cuts should be made in the beginning of the growing season in order to adequately manage the rapid growth and accumulation of forage, especially for the tall-growing warm-season grasses.