Urea (200 μg urea-N/g soil) was completely hydrolyzed within 20–56 h in alkaline, subtropical soils of India. Michaelis constant (Km) values varied from 2.0–32.0 X 10-3M, and urease activity (μg urea-N hydrolyzed/g soil/h) ranged from 3.5–10.0. Urease activity was correlated significantly with organic carbon (r = 0.8), but was not significantly correlated with clay (r = 0.45) and pH (r = −0.54). Added urease was deactivated after 96 h of incubation. High pH and free ammonia, resulting from rapid urea hydrolysis, caused accumulation and presistence of nitrites in soils receiving high rates of urea.