Herbage Accumulation, Nutritive Value, and Tillering Dynamics of Bahiagrass Genotypes Under Grazing Intensities.

Because existing bahiagrass (Paspalum notatum Flügge) cultivars are photoperiod sensitive, they produce minimal herbage during the cool season. Novel bahiagrass germplasm has been selected for lower daylength sensitivity and greater cold tolerance (termed PCA; less photoperiod sensitive, cold adapted), resulting in superior cool-season yields in the southern USA. However, cool-season productivity may jeopardize sward persistence. Therefore, evaluation of new genotypes (‘Florida Hay’, and two PCA types ’UF-Riata’ and ’FL Cycle 5’) under grazing is needed.

The performance of new genotypes UF-Riata, FL Cycle 5, and Florida Hay was compared with that of established cultivars ’Pensacola’ and ’Tifton 9’ during 2 yr (2009 and 2010), under mob-grazing. Small pastures (36 m²) were maintained under rotational stocking by cattle, with entrance height of 30 cm and stubble height either 8 or 16 cm. The 10 factorial treatment combinations (five genotypes x two stubble heights) were arranged in three replications of a randomized complete block design. Pasture productivity was characterized in terms of total herbage accumulation (kg DM ha^-1 yr^-1), and herbage nutritional value was compared in terms of crude protein and in vitro digestibility. Changes in tiller density (tillers m^-2) and mass (g tiller^-1) were compared to the theoretical expectations from the self-thinning rule that relates such variables.

Results from the first year suggest that UF-Riata and FL Cycle-5 herbage is as digestible as existing cultivars. Herbage CP was greater under the 16-cm stubble height for all entries, but no entry differences were noticed within grazing treatments. There was little variation in total DM accumulation when pastures were under the 8-cm stubble treatment, but under the 16-cm treatment, Florida Hay and UF-Riata outperformed the others. Tillering dynamics from the first year agree with current literature, and suggestions regarding persistence of the novel genotypes will arise from 2010 data.