Overseeding Eastern gamagrass with cool-season grasses or grass-legume mixtures
Type of DegreeMaster's Thesis
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The first year and a half of a 2-yr study was conducted at Black Belt Research and Extension Center in Marion Junction, AL to evaluate the effects of overseeding early- vs. late-maturing cool-season forages on forage production, nutritive value, and persistence of Eastern gamagrass (Tripsacum dactyloides). The cool-season component compared four overseeding treatments: control, early-maturing ‘Florida 401’ rye (Secale cereale), mid-maturity ‘Wrens Abruzzi’ rye, and a mixture of ‘Wrens Abruzzi’ plus ‘AU Red Ace’ red clover (Trifolium pratense). During the warm season, plots were fertilized with either 67 kg nitrogen (N)/ha or 135 kg N/ha. Measurements of pre-graze forage mass, herbage harvested, and herbage accumulated were calculated from pre- and post-graze forage samples during both seasons. Hand-plucked samples were collected to determine nutritional value. Ground cover estimations and frequency ratings were taken during months in which Eastern gamagrass was breaking dormancy to determine effects of overseeding on persistence of Eastern gamagrass. The same measurements were taken as Eastern gamagrass began to go dormant at the end of the summer. Mob-stocking was used to simulate rotational grazing every 28 days. Data were analyzed using the MIXED procedure in SAS 9.4, and differences were declared significant when P < 0.05. Overseeding with ‘Wrens Abruzzi’ rye with or without red clover allowed for greater forage mass (P = 0.0355) and greater digestibility (P = 0.0012) compared with Florida 401 rye, but all treatments provided high-quality forage for grazing throughout the winter. Overall forage accumulation during the cool-season months was low (2,077 and 2,184 kg DM/ha in Yr 1 and Yr 2, respectively) during both years of the evaluation. Warm-season results in Yr 1 indicate that harvest date had an effect on pre-graze forage mass (P = 0.0002) and forage accumulation (P = 0.0008), but N fertilization rate did not affect forage production of Eastern gamagrass (P = 0.1610). Forage mass peaked in June, then decreased through the late summer. Increasing N fertilization rate resulted in greater digestibility (P = 0.0264) and CP concentrations (P =0.0006) of Eastern gamagrass. Estimates of Eastern gamagrass ground cover and frequency of occurrence increased to 81% and 99%, respectively, over the summer growing season, which suggests that overseeding during the winter months did not impact persistence of Eastern gamagrass. A second year of the warm-season portion of this study is currently being conducted.