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Lookup NU author(s): Dr Elizabeth Stockdale
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Nitrogen (N), phosphorus (P) and potassium (K) budgets were calculated for nine organic farms in the UK. The farms were situated on sandy loams, silty clay loams and silty loams over chalk with stockless farming systems and cattle, pig and poultry enterprises with a significant proportion of arable cropping. A soil surface nutrient budget was calculated for the target rotation on each farm using information about field management and measurements of the soil, crops and manure. Losses of N through leaching and volatilization were calculated independently using the nitcat and manner models. Nutrient budgets for seven of the farm rotations showed an N surplus, six a P surplus and three a K surplus. The ratio of N inputs supplied in the form of biological fixation : manure : atmospheric deposition was approximately 2 : 2 : 1 for stocked systems and 2 : 0 : 1 for stockless systems. Phosphorus surpluses resulted from supplementary P fertilizer (rock phosphate) and additional feed for non-ruminant livestock. The stockless system without P fertilizer resulted in a large P deficit and stocked systems, which relied on recycling manure alone, a small P deficit. Only rotations with large returns of manure or imported feed showed a K surplus or a balanced K budget.
Author(s): Stockdale EA; Berry PM; Sylvester-Bradley R; Philipps L; Smith KA; Lord EI; Watson CA; Fortune S
Publication type: Article
Publication status: Published
Journal: Soil Use and Management
Year: 2003
Volume: 19
Issue: 2
Pages: 112-118
ISSN (print): 0266-0032
ISSN (electronic): 1475-2743
Publisher: Wiley-Blackwell Publishing Ltd.
URL: http://dx.doi.org/10.1079/SUM2003176
DOI: 10.1079/SUM2003176
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