Response of Soil Microorganisms and Enzymes Activity to Application of Buctril Super (Bromoxynil) under Rainfed Conditions.

A field experiment was conducted for two years to assess the impact of buctril super herbicide application on soil enzymes activity and microbial population. The hypothesis of the study was that the herbicide has negative effects on soil microbes and enzymes. The experiment was laid out in randomized complete block design using five herbicide treatments: 375 mL ha-1, 750 mL ha-1, 1500 mL ha-1, 2250 mL ha-1 and control with four replications. Wheat variety Chakwal-50 was sown as a test crop and the herbicide was applied seven days after sowing. The soil samples were taken at 0, 7, 15, 30 and 60 days after herbicide application. Results showed 30% decrease in bacterial population, 23.4% decline in actinomycetes population, 34% decrease in fungi population, 30% reduction in urease activity, 36% inhibition in dehydrogenase activity and 34% decline in alkaline phosphatase activity with bromoxynil herbicide application at 2250 mL ha-1 during the year 2011-2012. However, 36, 27.7, 38.6, 31, 36 and 31% decline in bacteria, actinomycetes, fungi population, urease, dehydrogenase and alkaline phosphatase activity was observed, respectively where the herbicide was applied at 2250 mL ha-1 during the year 2012-2013. Overall bacteria, actinomycetes and fungi populations showed decreasing trend with herbicide application up to the day-15 and then increasing trend was observed till day-60. Decrease in dehydrogenase and alkaline phosphatase activities was experienced with herbicide application upto day-7, thereafter the activities of these enzymes showed increasing tendency up to day-60 during both years. Buctril super herbicide had negative effects on soil microbes and enzymes activity showing significant reduction in these parameters up to two weeks after its application, which later on subsided. © 2015 Friends Science Publishers [ABSTRACT FROM AUTHOR]