Unique Dairy Applications of Eastern Gamagrass Forages in Central Wisconsin: I. Yield Potential
2010
Coblentz, Wayne K. | Jokela, William E. | Hoffman, Patrick C. | Bertram, Michael G.
Replacement dairy heifers (Bos taurus) offered diets comprised largely of corn (Zea mays L.) silage or other high-energy forages often become overconditioned, which may damage their future performance as lactating cows. Our objective was to assess the yield potential of a perennial C4 grass, eastern gamagrass [Tripsacum dactyloides (L.) L.], for incorporation into fiber-demanding, dairy-heifer or dry-cow diets. Replicated field plots of ‘Pete’ eastern gamagrass were evaluated within nine harvest systems and four N fertilization regimes. For single-harvest systems, dry matter (DM) yields increased across harvest dates, reaching numerical maximums of 7192, 9764, and 7554 kg ha⁻¹ 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⁻¹) between early and mid-August during 2008 and 2009 suggest that better yields could be achieved by delaying single harvests of eastern gamagrass beyond mid-August. Yields of DM from double-harvest systems were not competitive with single-harvest systems timed in mid-August. Nitrogen fertilization increased (P < 0.001) DM yields, exhibiting both linear (P < 0.001) and quadratic (P = 0.027) effects of application rate. However, efficiency of N usage was reduced as fertilization rates increased.
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