Grazing intensity effects on sward responses of UF Riata Bahiagrass

Abstract

Bahiagrass (Paspalum notatum Flüggé) is a rhizomatous, perennial, warm-season forage widely grown in the southeastern United States "UF Riata" bahiagrass is more upright growing with greater herbage production when days are shorter compared with most other cultivars. Lesser daylength sensitivity extends the grazing season, but in combination with more upright growth may negatively affect persistence under grazing, especially if out-of-season herbage production interferes with normal reserve storage. This 3-year study investigated above and belowground sward responses of UF Riata bahiagrass to three levels of post-grazing herbage mass (HM) (500 [heavy grazing, HG], 1500 [moderate grazing], or 2500 [light grazing, LG] kg DM ha−1, where DM is dry matter) imposed by mob stocking every 14 days. Total herbage accumulation (HA) and HA rate were not affected by treatment. Crude protein (CP) was affected by treatment × grazing cycle × year, whereas in vitro digestible organic matter concentrations were affected by treatment × year and grazing cycle × year. Root–rhizome biomass (12,940–9230 kg OM ha−1, where OM is organic matter) and soil cover percentage (97%–93%) decreased linearly as grazing intensity increased from LG to HG. Proportion of non-planted grasses was 34% and 17% in HG and LG swards, respectively. Proportion of non-grass weeds increased across treatments from 2% to 22% over the years. Moderate grazing could maintain similar CP to HG, and similar root–rhizome biomass to LG. Thus, considering both sward persistence and forage nutritive value, a target post-grazing HM of ≈1500 kg DM ha−1 is recommended when UF Riata pastures are grazed every 2 weeks.