Urease activity exhibited the same behaviour as those of the APA and ASA .
however, the UA increased rapidly and reached a maximum activity after 15 days for all treatments ; then the UA decreased significantly unit the end of the incubation period.
the UA is involved in the hydrolysis C-n bonds of some amides and urea.
the highest values of UA were observed in soil amended with low C:N ratio and high doses of sludge, probably due to the UA it a constitutive-intracellular enzyme and consequently it increases or decrease proportional to microbial biomass