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Relationships between Sorption and Desorption of Phosphorus by Soils
Author(s) -
Ballaux J. C.,
Peaslee D. E.
Publication year - 1975
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/sssaj1975.03615995003900020017x
Subject(s) - sorption , soil water , desorption , chemistry , adsorption , phosphorus , langmuir , environmental chemistry , soil test , soil science , analytical chemistry (journal) , environmental science , organic chemistry
A routine soil test can indicate the level of extractable P in the soil and the fertilizer P requirement if the test is calibrated for that soil type. Without calibration data, the test will indicate only the level of extractable P. The limited amount of calibration data could be extended more accurately over ranges of soils if soils could be categorized according to their capacities for sorption‐desorption of P. Relationships between the sorption and desorption of P were investigated for five soils ranging in clay content from 16 to 51%. Langmuir adsorption isotherms for some soils were curvilinear when the P concentration in the equilibrium solution was >10 µg/ml. To evaluate sorption at higher concentrations of P, values of adsorption maxima ( b ) and indices of bonding energy ( k ) were estimated from tangents to six segments of each isotherm. Within each soil, the six pairs of b and k values were related according to the equation k = ( a/b ) n , where n was a unique characteristic for each soil. Desorption was measured by adding P to soils, incubating, then extracting with anion exchange resin. The relative increases in extractable P among the five soils was highly correlated ( r = 0.99**) with values of n for the soils. Decreasing n values among soils indicated greater sorption capacities and lower tendencies to release P. Neither b nor k were consistently correlated with the relative increases in extractable P. The data suggest that n may provide an index of the sorption‐desorption properties of soils for grouping them on the basis of their reaction with added P and its subsequent release.