9Powell J M, Douglas B Jackson-Smith, Satter L D.Phosphorus feeding and manure nutrient recycling on Wisconsin dairy farms. Nutrient Cycling in Agroecosysterns, 2002, 62: 277-286.
10Ulan B, Bechmann M, Falster J, Jarvie H P, Tunney H. Agriculture as a phosphorus source for eutrophication in the north-west European countries, Norway, Sweden, United Kingdom and Ireland: a review. Soil Use and Management, 2007, 23(Sl): 5-15.
