Chemical nature and distribution of soil organic phosphate in two chronosequences of soils

Abstract

A method for the extraction of organic phosphate (Po) from soils was developed and used for the examination of samples from two chronosequences of soils. The total Po content of each soil from the Manawatu and Franz Josef chronosequences was obtained and the results compared with those obtained by the ignition method and some other extraction procedures. The danger of hydrolysis of Po to inorganic P was checked with model phosphate esters and soil extracts.

Fractionation of soil extracts was achieved with both ion exchange resin and Sephadex Gel techniques. The fractionation schemes revealed the presence of inositol phosphates, phospholipids , nucleic acids and humic acid-associated Po. Estimates of the amounts of Po in these four categories were made, along with total Po measurements, in relation to the age of the soils in the two chronosequences.

Four methods for obtaining the inositol phosphate content of soils were compared. A procedure for measuring the phospholipid content of soils by Soxhlet extraction was developed and compared with standard methods.