Effect of Harvest Dates on Yield Nutritive Value of Eastern Gamagrass

Yield of 'Pete' eastern gamagrass [Tripsacum dactyloides (L.) L.] was evaluated for 3 yr. Forage samples were harvested at 7-d intervals beginning on May 15 and ending on July 17 during 2000, 2001, and 2002. Samples from 2000 and 2001 were analyzed to determine nutrient composition. Plant height increased (P < 0.01) during the 10-wk sampling period by 132, 89, and 132 cm and maximum height reached 225, 231, and 240 cm during 2000, 2001, and 2002, respectively. Increases in DM yield over harvest dates were quadratic, linear, and cubic (P < 0.01) and ranged from 1.25 to 10.04, 4.14 to 14.51, and 2.15 to 15.19 Mg/ha during 2000, 2001, and 2002, respectively. Concentration of NDF for whole-plant samples increased (P < 0.02) and from 65.9 to 78.5% with advancing plant maturity in 2000 from 65.0 to 70.5% in 2001. The concentration of ADFincreased (P < 0.001) from 31.1 to 44.5% in 2000 and from 35.3 to 41.5% in 2001, respectively. The CP concentrations declined (P < 0.002) from 14.4 to 6.3% and 14.7 to 6.6% during 2000 and 2001, respectively. The least numerical value for fraction A (the immediately soluble portion) and the potential extent of DM degradability were observed with eastern gamagrass that was harvested in early July. With limited fertilization, eastern gamagrass demonstrated a tall growth habit and excellent DM yields. If hay of greater nutritive value is preferred for animals with greater nutrient requirements, then harvest should occur at the beginning of June.