SUMMARYGiven the finite nature of global phosphorus (P) resources, there is an increasing concern about balancing agronomic and environmental impacts from P usage on dairy farms. Data from a 3-year (2009–2011) survey were used to assess farm-gate P balances and P use efficiency (PUE) on 21 intensive grass-based dairy farms operating under the good agricultural practice (GAP) regulations in Ireland. Mean stocking rate (SR) was 2·06 livestock units (LU)/ha, mean P surplus was 5·09 kg/ha, or 0·004 kg P/kg milk solids (MS), and mean PUE was 0·70. Phosphorus imports were dominated by inorganic fertilizer (7·61 kg P/ha) and feeds (7·62 kg P/ha), while exports were dominated by milk (6·66 kg P/ha) and livestock (5·10 kg P/ha). Comparison to similar studies carried out before the introduction of the GAP regulations in 2006 indicated that P surplus, both per ha and per kg MS, has significantly decreased (by 74 and 81%, respectively) and PUE increased (by 48%), mostly due to decreased inorganic fertilizer P import and improvements in P management. There has been a notable shift towards spring application of organic manures, indicating improved awareness of the fertilizer value of organic manures and good compliance with the GAP regulations regarding fertilizer application timing. These results suggested a positive impact of the GAP regulations on dairy farm P surplus and PUE, indicating an improvement in both environmental and economic sustainability of dairy production through improved resource use efficiencies. Such improvements will be necessary to achieve national targets of improved water quality and increased dairy production. Results suggest that optimizing fertilizer and feed P imports combined with improved on-farm P recycling are the most effective way to increase PUE. Equally, continued monitoring of soil test P (STP) and P management will be necessary to ensure that adequate soil P fertility is maintained. Mean P surplus was lower and PUE was much higher than the overall mean surplus (15·92 kg P/ha) and PUE (0·47) from three studies of continental and English dairy farms, largely due to the low import system that is more typical in Ireland, with seasonal milk production (compact spring calving), low use of imported feeds and high use of grazed grass.

中文翻译：

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爱尔兰南部 21 个集约化草基奶牛场的磷平衡和利用效率

摘要鉴于全球磷 (P) 资源的有限性，人们越来越关注平衡奶牛场使用磷对农艺和环境的影响。一项为期 3 年（2009-2011 年）的调查数据用于评估爱尔兰 21 个在良好农业规范 (GAP) 法规下运营的集约化草基奶牛场的农场门口磷平衡和磷利用效率 (PUE)。平均放养率 (SR) 为 2·06 牲畜单位 (LU)/ha，平均 P 过剩为 5·09 kg/ha，或 0·004 kg P/kg 乳固体 (MS)，平均 PUE 为 0·70 . 磷的进口以无机肥料（7·61 kg P/ha）和饲料（7·62 kg P/ha）为主，出口以牛奶（6·66 kg P/ha）和牲畜（5·10 kg）为主亩/公顷）。与 2006 年引入 GAP 法规之前进行的类似研究的比较表明，P 盈余，每公顷和每公斤 MS 均显着下降（分别下降 74% 和 81%），PUE 增加（48%），主要是由于无机肥料 P 进口减少和 P 管理改进。有机肥在春季施用方面发生了显着转变，这表明人们对有机肥肥料价值的认识有所提高，并且很好地遵守了 GAP 关于施肥时间的规定。这些结果表明 GAP 法规对奶牛场 P 盈余和 PUE 产生了积极影响，表明通过提高资源利用效率改善了奶制品生产的环境和经济可持续性。这些改进对于实现改善水质和增加乳制品产量的国家目标是必要的。结果表明，优化肥料和饲料磷的进口以及改进农场磷回收是提高 PUE 的最有效方法。同样，有必要继续监测土壤测试磷（STP）和磷管理，以确保维持足够的土壤磷肥力。来自大陆和英国奶牛场的三项研究的平均 P 盈余较低且 PUE 远高于总体平均盈余 (15·92 kg P/ha) 和 PUE (0·47)，这主要是由于低进口系统，即在爱尔兰更为典型，具有季节性产奶量（紧凑型春季产犊）、进口饲料使用率低和放牧草的高使用率。有必要继续监测土壤测试磷（STP）和磷管理，以确保保持足够的土壤磷肥力。来自大陆和英国奶牛场的三项研究的平均 P 盈余较低且 PUE 远高于总体平均盈余 (15·92 kg P/ha) 和 PUE (0·47)，这主要是由于低进口系统，即在爱尔兰更为典型，具有季节性产奶量（紧凑型春季产犊）、进口饲料使用率低和放牧草的高使用率。有必要继续监测土壤测试磷（STP）和磷管理，以确保保持足够的土壤磷肥力。来自大陆和英国奶牛场的三项研究的平均 P 盈余较低且 PUE 远高于总体平均盈余 (15·92 kg P/ha) 和 PUE (0·47)，这主要是由于低进口系统，即在爱尔兰更为典型，具有季节性产奶量（紧凑型春季产犊）、进口饲料使用率低和放牧草的高使用率。