Department of Agricultural Chemistry, Soil Science and Biochemistry, Orissa University of Agriculture and Technology, Bhubaneswar, Orissa, 751003.
Urea super granule (USG) containing 3.958 x 10−4 kg N was displaced by 0.02 M Caso, solution in a soil column (0.09 m long) containing a sandy loam soil. The leachate fractions were collected periodically for the determination of NH2-N, NH4+-N and NO3−-N. The results showed that NH2-N was leached down to the extent of 53.2 per cent of applied USG in 40 h. The rate constant for USG hydrolysis was computed to be 0.023 h−1 at 27.5°C. The rate of movement of NH2-N was slower (3xl0−3 m h−1) than that of the water (4x10−3), but faster than that of NH4-N during the displacement. Ammonium was present as a dominant ion in soil due to greater adsorption and lower nitrification. The adsorption of NH4-N in soil was found to be linear, with the NH4+-N distribution coefficient of 17.2 during leaching.
USG, hydrolysis rate constant, NH4+-N distribution coefficient, leaching
