Regionalized Levels of Soil Phosphorus and Phosphorus Saturation in Beef Cattle Pastures with and without Grazing.

Available soil phosphorus (P) in various agro-ecosystems is regulated by climate, soil type, vegetation, and management practices. Available soil P in bahiagrass beef cattle pastures were compared with rhizoma peanut pastures and bermudagrass pastures. For each location, the main plot was represented by grazing management (grazing vs. no grazing) while forage type (bahiagrass vs. perennial peanut-bahiagrass mix at Brooksville, FL and bahiagrass vs. bermudagrass at Marianna, FL) represented sub-plot treatments. Soils were sampled concurrently from these locations (2004 to2007) with or without grazing. Soil available P concentration and the degree of soil P saturation varied  with pasture location (P≤0.0001), grazing management (P≤0.01), and forage type (P≤0.0001). There were interactions between pasture location and grazing management as well as between grazing management and forage type. Soil P concentration at Brooksville did not vary between grazed and non-grazed pastures but soil P concentration varied with forage type (peanuts, 25.1 mg/kg; bahiagrass, 19.3 mg/kg) with an interaction  between grazing management and forage type. At Marianna, soil P concentrations were greater in the non-grazed (11.3 mg/kg) than in the grazed (8.9 mg/kg) pastures. Based upon results from this study, pasture grazing by beef cattle appeared to have minimal (if any) effect on soil available P status.