Activity of enzymes in organic carbon-amended soils treated with varying levels of salts.

The effect of varying concentrations of either NaCl or Na2CO3 (0, 10, 20, and 25 meq/100 g soil) and organic carbon (0 and 2% starch) on the activity of dehydrogenase, urease, and phosphatase (nuclease) was studied in incubated samples of alluvial clay and calcareous sandy loam soils. Moisture content was kept at 60% W.H.C. The level of 10 meq/100 g soil of either sodium chloride or sodium carbonate was stimulatory for the activity of the three enzymes studied in both soils tested. The increasing concentrations of Na2CO3 showed greater changes in the enzymatic activity than the corresponding concentrations of NaCl in both soils. Application of starch reduced the inhibitory effect of the high levels of such salts on the enzymatic activities in both soils, except for phosphatase which was depressed by Na2SO3 in starch-amended soil samples. The calcareous soil responded to the starch addition less than the alluvial soil.