Productivity, nutritive quality and utilization of dallisgrass (Paspalum dilatatum) for beef cattle production as influenced by fertilization regime and grazing management.

摘要

Dallisgrass (Paspalum dilatatum) is well adapted to the Black Belt region of the southeastern US, and information on its productivity and nutritive quality as influenced by fertility and grazing management is needed in order to more fully develop its potential as a forage resource for the region. In each yr of a 2-yr study, an existing dallisgrass pasture that had been subdivided into 48 plots of 9.3 m2 each was fertilized with the equivalent of 34 (34N), 67 (67N), 101 (101N) or 134 (134N) kg N/ha from poultry litter (PL) or commercial fertilizer (CF; NH4NO 3). In both years, primary-growth and vegetative regrowth forage was harvested in mid-August and late September, respectively, and forage from each harvest was clipped to either a 5- or 10-cm stubble height. Forage cut to a 5-cm height yielded 71% more (P 0.001) DM than forage cut to a 10-cm height, but forage dry matter (DM) yields were not different between CF and PL treatments across years and fertilization rates. Concentration of crude protein (CP) was greater (P = 0.002) for CF than PL forage and increased for both fertilizer sources with increasing rates of N application. Forage concentrations of cell-wall constituents were not different between CF and PL treatments. Forage amended with CF had a higher concentration of Ca, Mg and Mn than PL-amended forage; however, forage amended with PL had a higher concentration of P and K than CF-amended forage. There was no effect of fertilizer source on forage concentration of Al, Cu or Zn. Results indicate that PL and CF were comparable for supporting productivity and nutritive quality of dallisgrass on Black Belt soils. In a 2-yr grazing experiment, replicate 0.40-ha paddocks in a dallisgrass pasture were continuously grazed (CG), or replicate 0.40-ha paddocks were subdivided into either two 0.20-ha, three 0.13-ha or four 0.10-ha cells and rotationally grazed (RG) by yearling beef steers. In 2007, there was no effect (P = 0.25) of grazing treatment on ADG. Steers grazing 0.10-ha, 0.20-ha and CG paddocks had 106 (P = 0.01), 86 (P = 0.03) and 83 (P = 0.03) kg greater total gain per ha (GPA), respectively, than steers grazing 0.13-ha paddocks. In 2008, there were no differences among treatments in ADG (P = 0.43) or areal liveweight gain ( P = 0.90). Correlation and regression analyses revealed positive statistical associations between steer performance and forage concentration of CP, areal mass of forage DM and areal mass of forage CP. Results indicate that productivity and quality of dallisgrass for stocker cattle production under intensive grazing management (forage allowance of ∼1 kg DM/kg steer liveweight) were comparable between continuous and rotational-grazing systems.