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Characterization of acid piedmont rice soils for phosphorus sorption and phosphorus saturation

Islam, M.A.; Saleque, M.A.; Karim, A.J.M.S.; Solaiman, A.R.M.; Masud, M.M.

Bulletin of the Institute of Tropical Agriculture Kyushu University 30: 11-27

2007


Accession: 022195565

The maximum phosphorus adsorption (S-max)and Phosphorous saturation index (P-max) of a soil provide information for the proper management of the P fertilizer of the soil. The objective of this investigation was to determine S-max and develop a P-sal for 14 rice soils. Soil samples were analyzed for pH, clay content, dithionite extractable Fe (Fe-D), Mehlich-3 (M3) extractable P (PM3), and Fe (FeM3). The S-max value and P-sal based on M3 extractions were determined. The S-max value ranged from 110 to 625 mg kg(-1), and correlated with sand (r=-0.70, P > 0.01), silt (r=0.70, P > 0.001, clay (r=0.59, P > 0.05) and Fe-D (r=0.71, P > 0.01). Soil pH(H2o) and organic carbon content were not correlated (P > 0.05) with S-max while pH(KCl) was negatively correlated (r=-0.64, P > 0.05) with S-max Multiple regression found that the combination of pH(KCl) and Fe were the two most important soil properties related to the S-max of the soils studied. Conventional adsorption equations, such as the Langmuir, Freundlich and Temkin equations, satisfactorily described the P sorption of the soils. The P sorption capacity of the studied soils varied from 80 to 316 mg kg(-1). The calculated energy of adsorption of the soils ranged from 0.18 to 1.56 mg L-1, and there was apparently a negative correlation between the energy of adsorption (k) and the observed S-max values. Buffering capacity ranged from 14 to 69. Phosphorus saturation indices (P-sal) of the tested soils varied from 1.92 to 28.21 %, and were correlated with sand (r=0.56, P > 0.05) and silt (r=-0.59, P > 0.05), but not with the other soil properties we studied.

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