Phosphorus desorption kinetics in relation to phosphorus forms and sorption properties of Portuguese acid soils
Type
article
Creator
Publisher
Identifier
MONTEIRO, M.C.H. and TORRENT, J. (2007). Phosphorus desorption kinetics in relation to phosphorus forms and sorption properties of Portuguese acid soils. Soil Science. 172(8):631-638
0038-075X
Title
Phosphorus desorption kinetics in relation to phosphorus forms and sorption properties of Portuguese acid soils
Subject
Phosphorus desorption
Phosphorus sorption
Acid soils
Olsen P
Phosphorus sorption
Acid soils
Olsen P
Date
2010-05-10T15:30:17Z
2010-05-10T15:30:17Z
2007
2010-05-10T15:30:17Z
2007
Description
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While much information exists on the quantitative relationships between phosphorus (P) sorption and soil properties, comparatively less attention has been given to the influence of soil properties and P forms on the kinetics of P desorption, and to the relationships between desorbable and sorbed P. The aim of this study was to rationalize the P desorption properties of a group of 29 acid soils representative of agricultural areas of Portugal. The soils differed widely in basic properties, total P concentration (91-1730 mg kg-1), Olsen P (2.5-116 mg kg-1), and relative contents of the ‘P fractions’ —defined operationally in accordance with the seven-step fractionation scheme of Ruiz et al. (1997). P sorption capacity was accurately predicted from the concentrations of oxalate-extractable Al and Fe, as is generally the case with acid soils. Desorption of sorbed P to an anion exchange resin could be described by a combination of two kinetic equations of the Michaelis-Menten type for fast and slowly desorbable P pools. Although the concentrations of both pools were correlated with those of various P fractions, they could not be unambiguously assigned to specific chemical P species. The high correlation found between fast desorbable P and Olsen P testifies to the usefulness of this agricultural P test for acid soils; however, Olsen P tended to overestimate and underestimate fast desorbable P for Olsen P values below and above ~80 mg kg-1, respectively. The average ratio of fast desorbable P to sorbed P was 0.21 and that of total desorbable P to sorbed P 0.60; both ratios increased with increasing degree of P saturation in the soil.
While much information exists on the quantitative relationships between phosphorus (P) sorption and soil properties, comparatively less attention has been given to the influence of soil properties and P forms on the kinetics of P desorption, and to the relationships between desorbable and sorbed P. The aim of this study was to rationalize the P desorption properties of a group of 29 acid soils representative of agricultural areas of Portugal. The soils differed widely in basic properties, total P concentration (91-1730 mg kg-1), Olsen P (2.5-116 mg kg-1), and relative contents of the ‘P fractions’ —defined operationally in accordance with the seven-step fractionation scheme of Ruiz et al. (1997). P sorption capacity was accurately predicted from the concentrations of oxalate-extractable Al and Fe, as is generally the case with acid soils. Desorption of sorbed P to an anion exchange resin could be described by a combination of two kinetic equations of the Michaelis-Menten type for fast and slowly desorbable P pools. Although the concentrations of both pools were correlated with those of various P fractions, they could not be unambiguously assigned to specific chemical P species. The high correlation found between fast desorbable P and Olsen P testifies to the usefulness of this agricultural P test for acid soils; however, Olsen P tended to overestimate and underestimate fast desorbable P for Olsen P values below and above ~80 mg kg-1, respectively. The average ratio of fast desorbable P to sorbed P was 0.21 and that of total desorbable P to sorbed P 0.60; both ratios increased with increasing degree of P saturation in the soil.
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Language
eng
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