Nitrate Leaching from Soils as Influenced by Rate and Timing of Potassium Nitate Application

Abstract

The kinetics of leaching of nitrate (NO3-) in agricultural and non-agricultural soils was studied on undistributed columns using alkaline soil (pH = 8) of Kota region of Rajasthan. Potassium nitrate (KNO3) was used as a source of NO3-. Power form equation (LRobs = k [NO3- ] i1.49 for agricultural and (LRobs = k [NO3- ] i1.72 for non-agricultural soils) have been derived for dependence of LRobs on leachable concentration of NO3- present initially in the column during leaching. Effects of pore volume, temperature, Ca hardness and Na level of extractants have been observed on leaching rate. Change in water filled porosity q (cm3cm-3) of the column has been found to affect LRobs. An increase in temperature in the range 25-50 °C has increased LRobs. Experimental data fitting on various kinetic models showed first order kinetic models and parabolic diffusion to be most suited for predicting leaching rates.