Amidase and urease activity in soil as affected by sludge,salinity and wetting and drying cycles

Three incubation experiments were carried out to assess the effect of different levels of sludge, salinity and of different wetting and drying cycles on amidase and urease activity in a calcareous silt loam soil. Both amidase and urease activities were largely increased with the increase in the amount of sludge applied. The addition of NH₄⁺ - N with sludge slightly reduced both activities. Addition of increasing amounts of a 1:1 NaCl: CaCl₂ salt mixture increasingly reduced the soil activities of amidase and urease. This effect was less severe in sludge amended soil. The data also showed that drying of either unamended or sludge amended soil cause a marked drop in amidase and urease activity. Rewetting increased both enzyme activities.