Effect of herbicides on the activity of soil enzymes urease in maize crop

A field experiment was conducted to study the effect of pre-emergence, post emergence and combination of atrazine with post emergence herbicides on soil enzyme urease activity(expressed as µg of NH4+ released g-1 soil h-1) at College Farm, College of Agriculture ,Professor Jayashankar Telangana State Agricultural University (PJTSAU), Rajendranagar, Hyderabad, India during kharif 2014. The experiment was laid out in randomized block design (RBD) using six herbicide treatments un weeded control and hand weeding at 20 and 40 DAS with three replications. Maize was sown as test crop(variety –DHM-117).The soil samples were collected at 15 days intervals ie: 0, 15,30,45, 60, 75 and 90 days, to assay the enzyme activity. The pre-emergence herbicides were sprayed at zero days after sowing where post- emergence herbicides were sprayed after 15 days after sowing. The enzyme activity in the control increased from 0 days to 60 days and then decreased but the activity in the pre- emergence herbicide pendimethalin showed the same phase as that of control and showed higher activity over the control at each stage where as atrazine showed decrease in activity at 0 days (8.71) and latter it revoked the activity and reached maximum at 60 days (12.35). When compare to pendimethalin the activity was less at each and every stage. In case of post – emergence herbicides the activity showed mixed responses to at different stages Tembotrione showed higher activity when compare to Topramezone. In combination of Tembotrione and Topramezone with atrazine showed mixed responses.