Effect of nickel contamination on soil enzymatic activities

The effect of soil contamination with nickel applied in the doses of 100, 200, 300 and 400 mg Ni/kg of soil on the activity of dehydrogenases, urease and acid and alkaline phosphatase was studied in a pot experiment. Heavy loamy sand and silty light loam were used in the experiment that comprised of two series: with spring barley cultivation and without plant cultivation. The enzyme activity was determined on day 14, 28, 42 and 56 of the experiment. Based on the study, it was found that soil contamination with nickel applied as NiCl2.6 H2O decreased the activity of dehydrogenases, urease and acid and alkaline phosphatase. This decrease was determined by the applied dose of this metal. Nickel exhibited a stronger effect on the soil with spring barley cultivation than on the unsown soil. In the heavy loamy sand sown with spring barley, more than 50% inhibition of the activity of dehydrogenases was caused by 300 and 400 mg Ni contamination, and in the case of urease by 200, 300 and 400 mg Ni/kg of soil. In the silty light loam sown with spring barley, more than 50% decrease in the activity of dehydrogenases and alkaline phosphatase was observed under 400 mg Ni contamination. The inhibition of the other enzyme activities did not exceed 50%. Urease and alkaline phosphatase exhibited a higher activity in the heavier soil, whereas dehydrogenases and acid phosphatase exhibited a higher activity in the lighter soil. In the nickel-free soil, spring barley cultivation had a positive effect on the enzyme activity and a positive correlation between the spring barley yield and the activity of dehydrogenases, urease and acid and alkaline phosphatase was observed.