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.

佛罗里达州的肉牛生产包括广泛管理的牛犊操作，其中将动物以最少的P输入量放养在原生和种植的牧场上。尽管有大量文献记载了牛犊牛系统的多种益处，但人们仍担心它们对水质的负面影响，特别是在生态敏感地区的磷。这项研究评估了使用以下方法管理的两个母牛犊牛操作的农场到大门的P平衡[Archbold's Buck Island Ranch（BIR）的3159公顷区域和佛罗里达牧场牛研究与教育中心（RCREC）的1170公顷]典型的区域做法。年平均磷输入量为2.4和2.1千克P ha - ¹ 年^-1BIR和RCREC分别以动物饲料为最大进口磷源（BIR和RCREC分别占总磷输入量的71％和42％）。两种操作的总磷产量相似（〜1.9 kg P ha ^-1  yr ^-1），并且大部分（77％）来自出售的动物。RCREC和BIR的估计P平衡几乎平衡（0.3和0.5 kg P ha ^-1  yr ^-1分别），主要是由于前几年肥料用量的大幅度减少。相对较高的企业效率（动物产品中磷产品相对于磷产品的投入比例； 81％至97％）表明，本研究评估的典型牛犊操作代表了环境可持续的土地管理。虽然提高养分效率是可持续农业的重要目标，但在低投入系统中实现中性平衡可能是不现实的，而低投入系统受天气和土壤遗留磷效应的季节性变化的影响很大。