Urease Activity and its Kinetics in Soil Treated with Tobacco Waste and Wheat Straw

This research was conducted to determine the effects of tobacco waste and straw incorporated to soil on urease activity and kinetics by an incubation experiment. For this purpose, clay loam soil sample and organic wastes were mixed until reaching 5% dry weight and this mixture was incubated in 25 +/- 0.5 degrees C temperature for 30 days. Following incubation period, urease activity and changing of kinetic parameters were searched in soil samples in different substrate concentrations (0,1,2,4,6,8,10 and 12%), incubation periods (0,1,2,3,4,5 and 6 hours) and incubation temperatures (0,10,20,30,40 and 50 degrees C). Research results showed that treatments of tobacco waste and wheat straw increased urease activity in soil. It was also determined that reaction velocity increased until the level of 8% substrate concentration for control and 10% for tobacco waste and wheat straw treatments. Then it did not change for both of them when exceeding these thresholds. The highest reaction velocity in all substrate concentrations was observed in 50 degrees C incubation temperature for all soil samples including control. In all treatments, the highest V-max and K-m values were measured between 40-50 degrees C. In addition, the highest V-max/K-m ratio for control and soil treated with organic wastes were observed in 50 degrees C and 40 degrees C, respectively.