Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 3/2/2010
Publication Date: 7/11/2010
Citation: Coblentz, W.K., Jokela, W.E., Bertram, M.G., Hoffman, P.C. 2010. Yield Potential of Eastern Gamagrass in Central Wisconsin. Journal of Dairy Science. 93:56. Interpretive Summary:
Technical Abstract: Recently, perennial warm-season grasses have received considerable interest, largely through bioenergy initiatives, but their suitability for limiting caloric intake by developing dairy heifers has not been explored. Our objective was to assess the yield potential of eastern gamagrass [Tripsacum dactyloides (L.) L.] for potential incorporation into dairy heifer diets offered throughout the north-central US. Replicated field plots of ‘Pete’ eastern gamagrass were evaluated within 9 harvest systems and 4 N fertilization regimes. Harvest systems included one-time harvests on 1 June, 15 June, 1 July, 15 July, 1 August, and 15 August, plus 3 two-cut harvest systems with harvests spaced at 45-d intervals (1 June/15 July, 15 June/1 August, and 1 July/15 August). Nitrogen fertilization was applied as ammonium nitrate (34-0-0) at rates of 0, 67, 134, or 202 kg N/ha annually. For 1-cut harvest systems, yields of DM increased across harvest dates, reaching numerical maximums of 7192, 9764, and 7554 kg/ha by mid-August of 2007, 2008, and 2009, respectively. During each year, there was a strong linear (P < 0.001) effect of harvest date; however, higher-ordered effects varied within year. Relatively large yield increases (= 1812 kg/ha) between 1 and 15 August during 2008 and 2009 suggest that improved yields could be achieved by delaying 1-cut harvests beyond 15 August. Yields of DM from 2-cut harvest systems were not competitive with 1-cut harvest systems timed in mid-August. Nitrogen fertilization rate affected (P < 0.001) yields of DM, but did not interact with other treatment effects (P = 0.082). Overall, yields of DM increased with N fertilization, exhibiting both linear (P < 0.001) and quadratic (P = 0.027) effects of rate, but efficiencies were reduced at the greatest application rates. Current recommendations for eastern gamagrass generally adopt a conservative philosophy concerning growth-reserve status; therefore, delaying a 1-cut harvest closer to first-frost may further improve yields, but also could negatively affect persistence. This approach for further increasing yields of DM might be viable, but it needs to be evaluated critically.