Analysis of total inositol phosphates in municipal solid waste compost-treated soils by two extraction methods

Humic substances are the most dynamic component of agricultural soils. In t his study, humic substances were extracted from soils based on standard aci d/base solubility and by gel filtration using Sephadex G25. Organic P is a component of humic substances, and inositol phosphates are considered to ha ve high prominence in organic P. The objectives of the study were to determ ine the effects of municipal solid waste (MSW) compost on the amount of ino sitol phosphates (IP) present in soils, and compare methods of extracting h umic substances from soils. Total IP (IPT) in soil extracts was determined following separation using a AG-1 x 8 anion exchange resin, acid digestion and ICAP analysis for P. The percentage of IP (%IP) of the total P in the s oil was also determined by colorimetric analysis. The soils were part of an experiment to study the effects of three rates of MSW compost and fertiliz ers on three crops grown in a Pugwash sandy loam (Humo-Ferric Podzol). The data were compared using ANOVA atP less than or equal to0.05; extraction me thods, fractions [humic/fulvic, high/low molecular (MW)], and five treatmen ts (three different rates of compost, fertilizer, and untreated soil) were compared. The gel filtration method extracted significantly more IPT and %I P than the solubility method. In the solubility method, humic and fulvic ac ids contained the same amounts of IPT and %IP, while the high MW fraction a lways contained more IPT and %IP than the low MW fraction in the gel filtra tion method. Fulvic acids and the low MW fraction contained similar amounts of IPT and %IP. There were differences in %IP between compost-treated soil s and the non-compost-treated soils, although there were no differences in IPT due to rate of compost addition.