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Field Test for Spodic Character Based on pH-Dependent Phosphorus Adsorption

Author:
Bartlett, R. J.
Source:
Soil Science Society of America journal 1972 v.36 no.4 pp. 642-644
ISSN:
0361-5995
Subject:
alizarin, aluminum, ammonium acetate, field methods, filtrates, phosphates, phosphorus, potassium chloride, sodium fluoride, soil sampling, spodic horizons
Abstract:
A field method based on P adsorption is proposed for measuring the relative amounts of reactive organic Al in suspected spodic horizons. A soil sample to be tested is equilibrated by shaking with a pH 9.1 phosphate solution. If high in reactive Al, the sample will remove the P from the solution as indicated by the absence of blue-colored molybdophosphate in the filtrate. Phosphorus adsorbed by soil samples under the test conditions was found to be correlated with Al extracted by pH 4.8 NH₄OAc, but not by neutral KCl. It is suggested that soils be initially screened for presence of reactive hydroxy Al by testing with NaF and alizarin yellow, with the expressed caution that occasional high organic spodic horizons may give negative NaF tests.
Agid:
6683852