The effect of cadmium on soil respiration, urease activity and nitrification in a vermicompost-enriched calcareous soil over time

Todaysoil pollution with heavy metals, especially cadmium due to its abundance in agricultural land has gained much more attention.In the present research, the effects of 0, 2 and 5 mg Cd kgˉ¹ soil were studied on soil respiration, mineralization of organic matter, urease activity and nitrification in a sandy clay loamsoil containing 2% vermicompost. Cadmium concentrations were examined in a factorial layout with a completely randomized design (CRD) with three replications under laboratory conditions during 3, 7, 31, 62 and 93 days. Before starting the experiment, the soil incubated for two weeks with vermicompost to achieve consistency in biological conditions. The results showed that cadmium had significant effect on the soil respiration and soil organic matter content but it did not have any effect on the specific activity of urease and soil nitrate concentration. On the other hand, the results revealed that incubation time had a significant influence on all determined parameters including specific activity of urease, soil respiration, the organic matter content and the nitrate concentration (P 0.01). The correlation coefficient between cadmium and examined parameters showed that cadmium treatment had no effect on urease activity and nitrification process and probably other soil properties affect the nitrification and urease activity in soil sample. Our results demonstratedthat among investigated factors soil respiration and organic carbon percentage are the most sensitive ones in treated cadmium concentrations.