Characterization of phosphorus in solutions from temperate soils
An analytical protocol for the determination of various soluble P fractions, namely: total dissolved P (TDP), dissolved reactive P (DRP), dissolved organic P (DOP) and dissolved condensed P (DCP) has been developed. The determination of DOP in soil solutions and water extracts was achieved by an improved automated photo-oxidation procedure, in which possible interferences caused by aluminium have been overcome. Partitioning of TDP into DRP, DOP and DCP fractions increased our understanding of P cycling in temperate soils. A combination of field and laboratory studies indicated that management factors such as soil acidity and fertiliser P additions greatly influenced the amount and distribution of soluble P between fractions. Natural climatic processes such as freeze/thaw and wetting/drying cycles have been shown to greatly affect soil P cycling. Fractionation of TDP into DRP, DOP and DCP components highlighted the problems associated with attributing the `freezing and drying effect' to any single process. The significance of these observations are discussed in terms of plant nutrition and possible contribution to P leaching and surface water quality.