Mihailescu E, Murphy P N C, Ryan W, Casey I A, Humphreys J
Animal and Grassland Research and Innovation Centre , Teagasc, Moorepark, Fermoy, Co. Cork , Ireland ; Department of Chemical and Life Sciences , Waterford Institute of Technology , Cork road, Waterford, Co. Waterford , Ireland.
School of Agriculture and Food Science , University College Dublin , Belfield, Dublin 4 , Ireland.
J Agric Sci. 2015 Apr;153(3):520-537. doi: 10.1017/S0021859614000641. Epub 2014 Sep 2.
Given 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.
鉴于全球磷（P）资源有限，人们越来越关注平衡奶牛场磷使用对农艺和环境的影响。利用一项为期3年（2009 - 2011年）的调查数据，评估了爱尔兰21家遵循良好农业规范（GAP）的集约化草地奶牛场的农场大门磷平衡和磷利用效率（PUE）。平均载畜率（SR）为2.06牲畜单位（LU）/公顷，平均磷盈余为5.09千克/公顷，或0.004千克磷/千克乳固体（MS），平均磷利用效率为0.70。磷进口主要来自无机肥料（7.61千克磷/公顷）和饲料（7.62千克磷/公顷），而出口主要来自牛奶（6.66千克磷/公顷）和牲畜（5.10千克磷/公顷）。与2006年GAP法规出台之前进行的类似研究相比，每公顷和每千克乳固体的磷盈余均显著下降（分别下降74%和81%），磷利用效率提高（提高48%），这主要是由于无机肥料磷进口减少以及磷管理的改善。有机肥施用已明显转向春季，这表明对有机肥肥料价值的认识有所提高，并且在肥料施用时间方面很好地遵守了GAP法规。这些结果表明GAP法规对奶牛场磷盈余和磷利用效率产生了积极影响，表明通过提高资源利用效率，奶牛生产的环境和经济可持续性均有所改善。要实现改善水质和增加奶牛产量的国家目标，这种改善是必要的。结果表明，优化肥料和饲料磷进口并结合改善农场内磷循环利用是提高磷利用效率的最有效方法。同样，持续监测土壤有效磷（STP）和磷管理对于确保维持足够的土壤磷肥力也是必要的。平均磷盈余低于大陆和英国奶牛场三项研究的总体平均盈余（15.92千克磷/公顷），磷利用效率则远高于总体平均磷利用效率（0.47），这主要是由于爱尔兰更典型的低进口系统，其牛奶季节性生产（紧凑的春季产犊）、进口饲料使用量低且放牧草使用量高。
