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Phosphorus Desorption Quantity‐Intensity Relationships in Soils
Author(s) -
Raven K. P.,
Hossner L. R.
Publication year - 1993
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1993.03615995005700060018x
Subject(s) - soil water , desorption , udic moisture regime , chemistry , subsoil , phosphorus , sorption , analytical chemistry (journal) , cation exchange capacity , soil test , environmental chemistry , mineralogy , soil science , adsorption , geology , loam , organic chemistry
Phosphorus desorption quantity‐intensity ( Q/I ) relationships reveal information about the P release properties of a soil. This research was carried out to evaluate the P desorption characteristics of a group of soils of diverse properties and to compare several empirical models to describe P desorption Q/I curves. Samples of five soils (Typic Calciustoll, Udic Pellustert, Vertic Albaqualf, and Aridic Calciustoll surface soils, and Psammentic Paleudult subsoil) were enriched with five P concentrations (0, 25, 50, 75, and 100 mg P kg −1 ) and incubated for 31 d. Subsamples of each treated soil sample were equilibrated with different amounts of HCO − 3 ‐saturated anion‐exchange resin. After 72 h the amount of P sorbed on the resin ( Q ) as well as the solution P concentration ( I ) were determined. Results from each subsample gave a point on the Q/I curve. The P release capacity of the soils used in this study was relatively low. In untreated samples, the solution P concentration when no P was desorbed ( I o ), an intensity parameter, ranged between <0.01 and 0.19 mg P L −1 , while the maximum desorbed soil P ( Q max ), a quantity parameter, was in the range 4.7 to 21.1 mg P kg −1 . The corresponding P buffering power index, the slope of the Q/I curve at I o , ranged between 56 and 1703 L kg −1 . These Q/I parameters were not closely related to any evaluated soil property, with the possible exceptions of CaCO 3 content in calcareous soils and clay content. The P buffering power of a soil apparently depended on the availability of P sorption sites and their degree of depletion, and was not always directly related to the ability of a soil to release P. The P release activity of a P‐enriched soil depended on the desorbability of the applied P as well as the native labile soil P. Plots of P buffering power against intensity for a given soil were not affected by P enrichment. The Q/I curves could be best described by a proposed desorption Q/I equation ( Q = a I −0.1 + b l n ( I + 1) + c ) and the Barrow power function, but the proposed equation followed the theoretical expected trend. The proposed equation is therefore recommended to describe P desorption Q/I curves.