The Effect of Cr(VI) and Vermicompost on Some of Microbial and Ecophysiological Indices of Soil

In this study, effects of heavy metal of chromium on microbial and eco physiological indices of soil in presence of vermicompost were evaluated using a complete randomized design. This experiment was carried out in five levels of chromium (0, 100, 200, 300 and 400 mg Cr kg-1 soil from potassium dichromate) and seven incubation periods (5, 30,60,90,100,110 and 120 days) in three replicates and for decreasing the adverse effects of pollutant in soil, in the 90th day, vermicompost was added to all of the treatments. At the end of each period, dehydrogenase enzyme activity, basal respiration and microbial biomass carbon as microbial indices and also metabolic and microbial quotient as eco physiological indices were measured. The results showed that with increasing chromium concentration in soil, the microbial indices were decreased up to the 90th day. Dehydrogenase enzyme activity decreased by 100 percent in concentrations of 100 mg Cr kg- and then it was increased, therefore application of the vermicompost compensated the adverse effects of the pollutant. Metabolic quotient in concentration of 300 mg kg- Cr the 90th day reached to 5.43 and then decreased to 0.164 in the 100th day. This decrease happened in concentration of 400 mg kg- Cr, severely. By adding organic matter, the microbial quotient increased 56 and 44 percent in control and in the highest concentration of the chromium respectively. Based on result of this research, in concentrations higher than 100 mg Cr kg- in soil negative effects of the metal on microbial indices was revealed and usage of vermicompost in improvement of this indices in presence of chromium was efficient.