Fractionation of P in soil as influenced by a single addition of liquid swine manure

Limited information exists as to the short-term effect of liquid swine manure on P distribution in soil. To address this issue, forms and distribution of inorganic P (P-i) and organic P (P-o) at 2 wk and 16 wk after manure addition were investigated through a sequential extraction procedure. An Orthic Black Chernozem was sampled from a field research plot (Dixon, SK) without previous manure and urea additions. Liquid swine manure and urea were applied at rates of 0, 100 and 400 mg N kg(-1). corresponding 10 and 40 mg P kg(-1) from manure. Manure addition did not increase the most labile P fractions in soil. Instead the initial fate of the P from the manure was mainly to enter moderately labile and stable fractions such as calcium phosphate and organic P forms. This is consistent with observations in the field that a single application of swine effluent does not have a large impact on extractable "available" P in the soil. Further studies are needed to determine how much manure P loading is required for saturation of the "fixed pool" of P in Saskatchewan soils.