Submitted to: Forage and Grazinglands
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/13/2014
Publication Date: 7/9/2014
Publication URL: http://handle.nal.usda.gov/10113/59361
Citation: Coblentz, W.K., Bertram, M.G., Hoffman, P.C., Esser, N.M., Cavadini, J.S. 2014. Fall harvest management of eastern gamagrass in central Wisconsin. Forage and Grazinglands. 10.2134/FG-2014-0016-RS. Interpretive Summary: Recent research suggests that eastern gamagrass may be an effective alternative to chopped straw which is commonly used in the blended diets of dairy heifers and cows to increase fiber and dilute energy density. Extension materials discussing appropriate fall management of eastern gamagrass often recommend avoiding harvest within six weeks of first frost. However, previous research has shown that single-harvest yields of dry matter are not maximized by mid-August in central Wisconsin because of inadequate accumulation of growing degree days. Our objectives were to evaluate dry matter yields, plant persistence, and nutritive value for eastern gamagrass harvested at 15-day intervals between August 1 and November 1. Single-cut harvests of eastern gamagrass on September 15 yielded 31% more dry matter than single-cut harvests occurring August 1. However, there was no evidence over four production years to suggest that plant persistence was affected by harvest dates scheduled after August 15. Producers can expect NDF concentrations (measure of fiber) for eastern gamagrass harvested between August 1 and October 1 to range narrowly from 75 to 80%; energy estimates (TDN) will likely hover around 50% TDN during this same time period. These nutritive characteristics are consistent with requirements for dilution of energy density and reduction of voluntary intake by replacement dairy heifers, and potentially for maintenance of proper rumen function within dairy cows offered high-concentrate diets. In central Wisconsin, single-cut harvests of eastern gamagrass as late as October 1 improved dry matter yields relative to earlier August harvest dates, and (more importantly) stand persistence was not affected. Results of this study will give producers the confidence to delay harvest of eastern gamagrass to increase yield knowing that this will not have a negative effect on the nutrient content or stand persistence of the grass.
Technical Abstract: Recent research has suggested that eastern gamagrass (EGG) may be an effective alternative to chopped straw in the blended diets of dairy heifers and cows. Extension materials discussing appropriate fall management of EGG often recommend avoiding harvest within six weeks of first frost. However, previous research has shown that single-harvest yields of DM are not maximized by mid-August in central Wisconsin; most likely this occurs because of inadequate accumulation of growing degree days by that date. Our objectives were to evaluate yields of DM, plant persistence, and nutritive value for EGG harvested at 15-d intervals between 1 August and 1 November. Yields of DM (2010 through 2013) increased with linear (P = 0.001) and quadratic (P < 0.001) effects over harvest dates, peaking at > 7400 kg/ha on 15 September and 1 October. Overall DM yields varied with year, but were greatest (P = 0.001) during the final year (2013) of the trial (7967 kg/ha). Percentage of continuous row coverage also was assessed, but was not affected by harvest date (P = 0.218). In central Wisconsin, single-cut harvests of EGG timed as late as 1 October improved DM yields relative to August harvest dates without compromising plant persistence.