Leaching mechanism of alkaline soil under phosphate application; a kinetic approach

Author(s): Bharatiy Sharma, Sweta Sexena, Meenaxi Vijay, Ashu Rani

The kinetics of leaching of phosphate has been studied on undistributed columns of alkaline soil (pH=8) ofKota region ofRajasthan India. Na2HPO4 has been taken as source of added phosphate. Initial leaching rates (LR obs) have been calculated using Latshaw method and linear power from equation (LRobs  k [PO4 3-]i 1.3) has been derived for dependence of LRobs on leachable concentration of phosphate present initially in the column during leaching. Various extractions viz. sodium bicarbonate, sodium oxalate, sodium citrate and water have been used to study leaching. Detailed kinetics has been followed with 0.5MNaHCO3 as extractant. Change in water filled porosity, , cm3 cm-3 of the column has not affected LRobs. An increase in temperature in the range 25-50oC increased LRobs. Experimental data on fitting on various kinetic models showed zero and first order kineticmodels to be most suited while parabolic diffusion and elovich equations were rejected.

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