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Isotopic Exchange Characteristics of Aluminum‐ and Iron‐bound Fractions of Soil Phosphorus
Author(s) -
Tandon H. L. S.,
Kurtz L. T.
Publication year - 1968
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/sssaj1968.03615995003200060027x
Subject(s) - soil water , chemistry , phosphorus , aluminium , environmental chemistry , soil science , geology , organic chemistry
The source of most of the isotopically exchangeable P in widely different soils was found to be in the Al‐ and Fe‐P fractions. The relative contribution of Fe‐P to exchangeable P was greater at longer exchange periods, showing that Fe‐P had more slowly‐exchangeable components than Al‐P. The rate of exchange of Al‐ and Fe‐P varied from 28 to 162 ppm/hr and 22 to 72 ppm/hr, respectively, in the first half‐hour and was in no case greater than 2 ppm/hr after 24 hours of exchange. Ratio of specific activities of Al‐ or Fe‐P were used to compare the surface activities of the P fractions. The term “Relative Activity Number” (ratio of specific activities of Al‐ to Fe‐P in a soil) is proposed as an index of the relative activity of Al‐ and Fe‐P. RAN for soils studied varied from 1.11 to 2.80 showing that Al‐P was 1.11 to 2.80 times as active as Fe‐P. RAN in soils which had received P was smaller than RAN in untreated soils showing greater exchangeability of the reaction products in the Fe‐P form. In a few soils as much as ½ to ⅔ of Al‐ and Fe‐P was not exchanged in 147 hours. Thus, a considerable proportion of these P fractions is relatively “inactive.”.