Urease present in the soil breaks the urea into ammonia and carbon dioxide. The maximum activity of the enzyme depends on the incubation periods . Enzyme activity was determined at different incubation periods as 5, 10-, 15-, 20-, and 30-min. Effect of different incubation periods on urease activity was determined by using combined inhibitors A1, A2, A3 in the ratio of 1:1, 0.25:0.75, and 0.75:0.25 with 0.50% concentration against Faisalabad, Gujranwala, and Sheikhupura cultivated soil (see Fig. ). At 5 min of the incubation period, the activity of urease in control was recorded as 23.03, 26.28, and 26.82 IU/g soil for Faisalabad, Gujranwala, and Sheikhupura cultivated soil respectively. While the soil treated samples with A1, A2, and A3 inhibitors showed the urease activity of 6.75, 3.83, and 7.06 IU/g soil for Faisalabad, 10.78, 16.51, and 7.06 IU/g soil for Gujranwala, and 11.07, 9.01, and 9.26 IU/g soil for Sheikhupura soil respectively at 5 min incubation time and 0.50% concentration (see Fig. ).