Influence of Organic Manure on Organic Phosphorus Fraction in Soils

The transformation of organic P (Po) from organic manures in two types of soils (ultisol and entisol) and the influences of external addition of organic substance or inorganic P (Pi) on Po under the condition of the 60% maximum water capacity were investigated. The results obtained from Po fractionation experiments indicated that all the Po fractions except for the highly resistant Po fraction decreased during incubation. Application of pig feces and cow feces could largely increase each fraction of Po in the soils. Immediately after application of organic manure into the soils a large part of labile and moderately labile Po from organic manure was transferred into moderately resistant Po, which might be due to the fact that Ca- or Mg-inositol P was precipitated into Fe-inositol P. However, the availability of Po from organic manure in the soils would increase again after incubation because of the transformation of moderately labile and resistant Po fractions into labile Po fractions. Addition of cellul