The high urea concentrations caused a considerable pH change in the soil. The effect of pH on urease activity in soils was studied in buffered urea solutions. Urea hydrolysis consumes two protons (H + ) for each mole of urea hydrolyzed. This reaction tends to increase the pH around urea-granules, and thus increases the rate of urea hydrolysis . Fig. ) presented the results of the effect of pH on A1, A2, and A3 inhibitor combinations against all three districts (Faisalabad, Gujranwala, and Sheikhupura). Similarly, the minimum enzyme activity of about 1.71, 6.82, and 5.66 IU/g soil was noted for Faisalabad cultivated soil, 7.21, 6.07, and 3.41 IU/g soil for Gujranwala, 1.31, 2.17, and 3.03 IU/g soil for Sheikhupura cultivated soil with A1, A2, and A3 combinations respectively, at pH value of 3.5 and 0.50% concentration. While the control presented 15.12, 12.25, and 9.93 IU/g soil inhibition value with the same reaction condition, which indicated. When soil pH increases to 6.5, the hydrolysis rate of urea increases, urease (optimum pH 6.67) showed maximum activity in control while applied inhibitors were found less active. At pH 7.5, the activity of urease decreased due to little conformational changes in their structure. Soares et al. revealed that 5% NBPT and DCD treated urea showed 28% reduction of NH3 and 74% of N recovery, while 10% NBPT and DCD treated urea disclosed 33 and 77% of NH3 reduction and N recovery respectively at pH value of 6.8 between 7-9 days of observation. Longo et al.