Variations in Soil Urease and Dehydrogenase Activities as Determined by Diuron, Pyrithiobac Sodium and Quizalofop Ethyl Applied to Cotton Cultivated in Red and Black Soils

Activities of soil enzymes viz., urease and dehydrogenase were studied in two field experiments conducted in red and black soils at Professor Jayashankar Telangana State Agricultural University, Rajendranagar during kharif, 2018. Different doses of diuron in combination with postemergence tank-mix application of pyrithiobac sodium + quizalofop ethyl were tested. Soil urease activity showed an increasing trend and it increased from the day of PE herbicide application to flowering. Highest urease activity was noticed at flowering stage and then after the activity decreased upto harvest. In diuron treatments, the urease activity decreased substantially upto 5 DAHS, which later increased at flowering. Significant differences were observed in urease activity among all the treatments from the day of PE application to the day of postemergence spray in both red and black soils. No significant difference was observed in urease activity due to application of postemergence herbicide in both red and black soils. No significant difference was observed due to the application of pre and postemergence herbicides on the activity of dehydrogenase in both red and black soils but the activity of dehydrogenase increased from the day of PE herbicide application to flowering, exhibited highest activity at flowering stage and there after the activity decreased at harvest in both red and black soils.