Impact of herbicide and various soil amendments on soil enzymes activities in a tropical rainfed agroecosystem

A two year study was designed to investigate the activities of soil enzymes namely β-glucosidase, alkaline phosphatase and urease in an agroecosystem under rice–wheat–summer fallow crop rotation receiving herbicide (HC) as Butachlor, either singly or in combination of soil amendments of varying resource quality. Chemical fertilizer (CF), Sesbania shoot (SS), farmyard manure (FYM) and wheat straw (WS), carrying equivalent amount of N were added in combination of HC to soil along with a no input control (CO). Throughout the annual cycle, the activity of β-glucosidase was maximum in HC + WS treatment followed by the decreasing order for HC + FYM > HC + SS > HC + CF > HC > CO plots. Almost similar trend was found for alkaline phosphatase activity throughout the annual cycle. Within the crop cycle, the activities of the two enzymes increased from the vegetative to grain forming stage and then decreased at crop maturity. By contrast, urease activity decreased constantly through the crop cycle for all the treatments except the HC + WS treatment. The interaction of herbicide with soil inputs irrespective of their resource quality compared to single application of herbicide increased activities of all the three enzymes throughout the annual cycle. The activity of β-glucosidase, alkaline phosphatase and urease was influenced by the C:N ratio of the various soil inputs.

► We estimated impact of herbicide and soil inputs on enzyme activities.
► Herbicide alone did not show any significant impact on enzymes activity.
► Activity of β-glucosidase, alkaline phosphatase & urease, influenced by C:N ratio of soil inputs.