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Evaluating the effectiveness of the phosphorus sorption index for estimating maximum phosphorus sorption capacity
Author(s) -
Bolster Carl H.,
McGrath Josh M.,
Rosso Emileigh,
Blombäck Karin
Publication year - 2020
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 - 10.1002/saj2.20078
Subject(s) - sorption , soil water , chemistry , phosphorus , langmuir , langmuir adsorption model , negative correlation , sorption isotherm , analytical chemistry (journal) , correlation , mathematics , adsorption , soil science , environmental chemistry , environmental science , organic chemistry , medicine , geometry
The single‐point P sorption index (PSI), which is defined as the ratio of sorbed P ( S ) to the log P concentration in soil solution following a single P addition, is often used to estimate maximum soil P sorption capacity ( S max ). Although studies have found good correlations between PSI and S max as determined from fitting the Langmuir model to complete sorption isotherm data, a thorough analysis of the role of added P concentration on this relationship is needed. Our first objective was to investigate the effect of added P concentration on the correlation between PSI and S max as determined by the Langmuir equation. Our second objective was to determine if S was better than PSI for predicting S max . Using numerical simulations, we tested the correlation between S max and PSI for added P concentrations of 75, 100, 150, and 200 mg P L −1 . Results of the simulations show that the strength of the correlation between S max and PSI increases with increasing P concentration. Our results also show that PSI was a better predictor of S max than S for added concentrations of 75 and 100 mg P L −1 , whereas at the higher rates S was a slightly better predictor of S max and gave a direct estimate of S max rather than the relative estimate obtained from PSI. Results from P sorption data measured on soils from Maryland and Sweden were consistent with our results from the numerical simulations. Our findings highlight important limitations of using PSI for estimating S max .