Ammonia can be lost from soil when urea is applied on the surface. A study in Malaysia looked at this loss in 22 different soils. They found that the amount of ammonia lost varied between soils, with most losing around 35% of the nitrogen applied. Acid sulfate soils had lower losses. The majority of the loss happened in the first 3-4 days after urea application. The activity of urease enzyme in the soils affected the amount of ammonia lost. Soil texture and carbon content did not impact urease activity.