Farm-scale phosphorus budgets of beef cow-calf operations

Abstract

Beef cattle production in Florida consists of extensively managed cow-calf operations where animals are stocked on native and planted pastures with minimal P inputs. Despite the extensive literature documenting multiple benefits of cow-calf systems, concerns exist regarding their negative impacts on water quality, especially P in ecologically sensitive areas. This study evaluated farm-to-gate P balance for two cow-calf operations [a 3159-ha section of Archbold’s Buck Island Ranch (BIR) and the 1170 ha University of Florida Range Cattle Research and Education Center (RCREC)] both managed using typical regional practices. Mean annual P inputs were 2.4 and 2.1 kg P ha−1 yr−1 in BIR and RCREC, respectively, with animal feed being the single largest source of P imported (71% and 42% of total P inputs in BIR and RCREC, respectively). Total P outputs were similar for both operations (~ 1.9 kg P ha−1 yr−1) and was mostly (77%) from sold animals. Estimated P balance was nearly balanced for both RCREC and BIR (0.3 and 0.5 kg P ha−1 yr−1, respectively), largely as a result of significant reductions in fertilizer inputs from earlier years. The relatively high enterprise efficiency (proportion of P outputs in animal product relative to P inputs; 81 to 97%) suggested that typical cow-calf operations as those evaluated in this study represent an environmentally sustainable land management. Although improving nutrient efficiency is an important goal for sustainable agriculture, achieving neutral balance may be unrealistic in low-input systems that are largely affected by seasonal variations in weather and soil legacy P effects.