Intensive dairy farming is implicated with the phosphorus (P) enrichment and eutrophication of fresh water bodies. In Northern Ireland (NI), although P surpluses on dairy farms are high, representative soil P data for both dairy and non-dairy ruminant sector grassland are needed to help assess the extent to which dairying per se is contributing to poor water quality. Data from a recently completed European Union funded NI-wide soil testing scheme were available to help in this assessment. A high proportion (50%) of dairy grassland was found to be over-supplied with P (>25 mg Olsen-P l soil⁻¹), but surprisingly, some 25% of more extensively managed non-dairy ruminant grassland was also over-supplied with P. This is possibly because fertilizer-P and/or manure-P is being spread and/or faeces excreted by out-wintered livestock on only a fraction of the grassland area, with most of the remaining land being too wet or too inaccessible for such management. Therefore, even though the P over-supply situation is most acute in the dairy sector, because the non-dairy ruminant sector occupies the majority (78%) of the ruminant grassland platform, it is responsible for almost two thirds (64%) of all P-enriched grassland soils across the ruminant sectors, and hence potentially poses a greater threat to water quality than the more intensive dairy sector. To address this newly recognized problem, farm-gate P surpluses may need to be redefined in terms of surplus P per unit of land suitable for manure-P application and/or out-wintering livestock, as opposed to land owned or managed, and a regulatory maximum limit applied to all ruminant farms regardless of their management intensity or stocking density.

中文翻译：

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乳制品和非乳制品反刍动物部门对草原土壤的 Olsen-P 状态以及北爱尔兰水质的相对影响

集约化奶牛养殖与淡水体的磷 (P) 富集和富营养化有关。在北爱尔兰 (NI)，尽管奶牛场的磷过剩很高，但需要奶牛和非奶反刍动物部门草地的代表性土壤磷数据，以帮助评估奶业本身对水质差的影响程度。最近完成的欧盟资助的 NI 范围土壤测试计划的数据可用于帮助进行此评估。发现高比例 (50%) 的奶牛草地过度供应 P（>25 mg Olsen-P l 土壤^-1)，但令人惊讶的是，约 25% 的更广泛管理的非乳反刍动物草地也过量供应磷。牲畜只在草原面积的一小部分，其余大部分土地太湿或太难进行此类管理。因此，尽管 P 供过于求的情况在奶业最为严重，但由于非奶类反刍动物部门占据了大部分（78%）的反刍草地平台，占了近三分之二（64%）的反刍动物部门的所有富含磷的草地土壤，因此可能比集约化的乳制品部门对水质构成更大的威胁。为了解决这个新发现的问题，