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Nitrogen and phosphorus output standards for farm livestock - WT0715NVZ

Farm manures are a major source of nitrogen (N) and phosphorus (P) pollution. Excreta from livestock make a significant contribution to atmospheric ammonia emissions and N and P losses from agricultural land to surface and ground water systems (leading to eutrophication and acidification). The UK Government is committed to reducing nutrient emissions from agriculture, to enable compliance with a number of EU Directives (e.g. Nitrate Directive, National Emissions Ceilings Directive, Water Framework Directive).

Data on manure N outputs/excretion have been published in the UK (Smith and Frost, 2000; Smith et al., 2000) and elsewhere in Europe (Anon, 2001) and these form the basis for setting environmentally acceptable stocking rates, as part of Nitrate Vulnerable Zone (NVZ) Action Programmes. However, the origins of the data are not always transparent, and it is not always clear whether the values quoted represent excreted N or output (i.e. adjusted for ammonia losses during housing and storage). The latter are more correctly indicative of N loading to land. Furthermore, many of the data used in estimating N ‘output’ by livestock were derived from feeding or production systems that were less intensive than those in operation today. As a result, data derived from these studies may not be applicable to current systems of production.

As part of a recent EC-funded project, a review of N output standards from a number of Member States was undertaken (Cottrill et al., 2005). This highlighted (i) the inconsistency of reporting N output data and (ii) differences from currently used ‘standards’. The review of standards proposed in this study would benefit from and build on the data accumulated as part of this EC study.

The N output figures published as part of the Defra “NVZ Action Programme” (Anon, 1998a) and within the Water Code (Anon, 1998b) are probably the most important and far-reaching, environmental statistics, as they control farm livestock stocking rates. The proposed review and updating of these standards is therefore an essential component of the revision of the NVZ Action Programme in England.

Phosphorus (P) excretion by farm livestock is a major cause of eutrophication of freshwater systems, and Defra has identified the reduction in P losses from agricultural land as a key objective in improving water quality. There are no current ‘official’ standards for P excretion, other than the guideline values published in RB209 (Anon, 2000). However, as with N, the European Commission has indicated a desire to set limits on P loadings to land and has called for recommendations for a common approach to establishing livestock P excretion standards across the EU. An initial approach was also examined within the EC study referred to above (Cottrill et al., 2005).
a) To review inconsistencies in the expression of current N output standards.
b) To review and update N output standards for farm livestock in the UK.
c) To evaluate the potential impact of ammonia losses during the housing and manure storage phases, on the proposed N output standards.
d) To propose standards of P excretion by farm livestock.

Project Documents
• Final Report : N and P outputs from Livestock Excreta   (1571k)
Time-Scale and Cost
From: 2005

To: 2006

Cost: £59,000
Contractor / Funded Organisations
Environmental Protection              
Water Quality              
Fields of Study
Water Quality