Response of Dehydrogenase and Urease to Tribenuron-methyl and Bromoxynil herbicides in soil under wheat cultivation

The purpose of this study was to investigate the effects of Tribenuron-methyl (Granstar) and Bromoxynil (Pardnr) herbicides on dehydrogenase and urease activity and biological properties of a calcareous soil under wheat cultivation. An experiment was conducted in a completely randomized design (CRD) with factorial arrangement (18 treatments) and 3 replications in pots. Tribenuron-methyl concentrations of 30، 42، 56 (concentration recommended) and 84 milligrams per liter and Bromoxynil concentrations of 225، 450، 675 (concentration recommended) and 900 milligrams per liter were applied into the soil samples in the presence and absence of wheat plants. The activities of soil dehydrogenase and urease were measured at 3، 30 and 60 days after herbicide application. The results showed that dehydrogenase and urease activities were reduced with increasing herbicides concentrations in each of the sampling time compared to the control treatment. The most reduction of dehydrogenase and urease activities (61% and 51% respectively) was observed at concentration of 900 milligrams per liter treatment after 3 and 30 days of application. Dehydrogenase activity was increased after three days and it might be due to an increase in microbial populations with the capability of utilizing the herbicides as a carbon source. Also، a significantly decrease observed in enzymatic activities in treatments without plants compared to the plant treatments.