Urea is the main form of nitrogen used in developing countries. An important drawback, however, for its use is the risk for NH₃ volatilization upon hydrolysis. Therefore, urease inhibitors have been used to slow down the hydrolysis. It was shown that in the aerobic, non-acid soil, the inhibition of NBPT > PPDA > HQ. In acid conditions, the difference between the inhibitors was not as obvious as it was in the non-acid soil. Under waterlogged conditions, PPDA is the most effective inhibitor. In general, if the inhibition is effective, less NH₄⁺ -N is produced, and less NO₂‾ plus NO₃‾  -N is subsequently formed. The amount of volatilized NH₃ is also lower.