UREASE ACTIVITY AND KINETICS OF UREA TRANSFORMATION IN SOILS

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Abstract
The effects of soil type, N concentration, organic matter, moisture regime, CaCO3, and temperature on urease activity and kinetics of urea transformation were studied in a series of laboratory incubation experiments. Urease activity ranged from 19.0 to 26.1 tig urea-N hydrolyzed/g soil/h at 37°C. Increase in N levels, temperature up to 35°C, and moisture content, up to field capacity linearly increased urease activity of three selected soils, and addition of CaCO3 up to 8% decreased it considerably. There was no effect of undecomposed grasses, but decomposed organic matter increased soil urease activity. Urea transformation followed first-order kinetics, and the rate of urea hydrolysis increased with temperature in the three soils. Thermodynamic properties (energy of activation, free energy, entropy) were calculated for selected soils. The effects of soil type, N concentration, organic matter, moisture regime, CaCO3, and temperature on urease activity and kinetics of urea transformation were studied in a series of laboratory incubation experiments. Urease activity ranged from 19.0 to 26.1 tig urea-N hydrolyzed/g soil/h at 37°C. Increase in N levels, temperature up to 35°C, and moisture content, up to field capacity linearly increased urease activity of three selected soils, and addition of CaCO3 up to 8% decreased it considerably. There was no effect of undecomposed grasses, but decomposed organic matter increased soil urease activity. Urea transformation followed first-order kinetics, and the rate of urea hydrolysis increased with temperature in the three soils. Thermodynamic properties (energy of activation, free energy, entropy) were calculated for selected soils. © Williams & Wilkins 1984. All Rights Reserved.
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