title: Are horse paddocks threatening water quality through excess loading of nutrients?
abstract: The Baltic Sea is one of the most eutrophied water bodies in northern Europe and more than 50% of its total anthropogenic waterborne phosphorus (P) and nitrogen (N) loads derive from agricultural sources. Sweden is the second largest contributor of waterborne N and the third largest contributor of waterborne P to the Baltic Sea. Horse farms now occupy almost 10% of Swedish agricultural land, but are not well investigated with regard to their environmental impact. In this study, potential P, N and carbon (C) leaching losses were measured from two representative horse paddock topsoils (0-20 cm; a clay and a loamy sand) following simulated rainfall events in the laboratory. Results showed that the leachate concentrations and net release of P, N and dissolved organic C (DOC) from paddock topsoils were highest in feeding and excretion areas and considerably higher from the loamy sand than the clay paddock topsoil. Leaching losses of dissolved reactive P (DRP) were significantly (p < 0.05) correlated with concentrations of water-soluble P and ammonium acetate lactate-extractable P (P-AL) in the soil, while leaching losses of dissolved organic P and total organic N were significantly correlated with DOC concentration in leachate. Leaching loads of P and N from paddock topsoils greatly exceeded average figures for Swedish agricultural topsoils. It was concluded that: i) horse paddocks pose a potential threat to water quality via leaching of excess P and N, ii) feeding and excretion areas are potential hotspots for highly enhanced leaching losses, and iii) paddocks established on sandy soils are particularly susceptible to high N leaching losses.
authors.affiliation: Department of Soil and Environment, Swedish University of Agricultural Sciences, Box 7014, SE-750 07 Uppsala, Sweden. Electronic address: masud.parvage@slu.se.
authors.forename: Mohammed Masud
authors.initials: MM
authors.lastname: Parvage
authors.affiliation: Biogeophysics and Water Quality, Department of Soil and Environment, Swedish University of Agricultural Sciences, Box 7014, SE-750 07 Uppsala, Sweden.
authors.forename: Barbro
authors.initials: B
authors.lastname: Ulén
authors.affiliation: Plant Nutrition and Soil Biology, Department of Soil and Environment, Swedish University of Agricultural Sciences, Box 7014, SE-750 07 Uppsala, Sweden.
authors.forename: Holger
authors.initials: H
authors.lastname: Kirchmann
mesh_terms: D000704:Analysis of Variance; D000822:Animal Husbandry / Q000379:methods; D000818:Animals; D006736:Horses; D006799:Housing, Animal / Q000706:statistics & numerical data*; D016014:Linear Models; D009584:Nitrogen / Q000032:analysis; D010758:Phosphorus / Q000032:analysis; D012987:Soil / Q000737:chemistry*; D013548:Sweden; D014874:Water Pollutants, Chemical / Q000032:analysis*; D060753:Water Quality / Q000592:standards*
chemical_list: D012987:Soil; D014874:Water Pollutants, Chemical; D010758:Phosphorus; D009584:Nitrogen
keywords: Animal grazing; Eutrophication; Horse keeping; Nitrogen and phosphorus; Nutrient losses