Effect of Conventional and Conservation Agriculture Practices on Dissipation of Metribuzin and Clodinafop-Propargyl, Soil Enzymatic and Microbial Activities in Wheat in a Rice-Wheat System

Abstract

ABSTRACT Soil enzymes and microbial activity are an indicator of soil quality for assessing the sustainability of agricultural ecosystems. The present study determined the persistence of metribuzin and clodinafop-propargyl and response of soil quality indicators to (1) conservation agriculture (continuous zero tillage and surface residue retention) and conventional agriculture (continuous tillage and removal/incorporation of residues) practices and (2) weed management practices in a wheat field under rice-wheat system. The shift from conventional to conservation agriculture practices increased the dissipation of metribuzin and clodinafop propargyl and significantly enhanced soil dehydrogenase (DHA) and urease activity. The residues of metribuzin and clodinafop in grain and straw samples from all treatment were below maximum residue limits (<0.01 µg g−1). Post-emergence application of clodinafop-propargyl plus metribuzin caused significant inhibition in DHA and urease activity at 7 days after treatment (DAT) compared to unsprayed control. However, from 31 DAT till crop harvest (115 DAT), herbicide treated plots had higher enzymatic activity than unsprayed plots. Intervention of one hoeing following herbicide application had greater stimulation in enzyme activity than sole herbicide. Conservation agriculture practices had higher colony development (CD) and ecophysiological (EP) indices than conventional agriculture practices for heterotrophic bacteria, fungi and actinomycetes. All tillage, residue and weed management practices had non-significant effect on alkaline phosphatase activity and phosphate solubilizers, in soil. Adoption of conservation agriculture practices along with integrated weed management seems to be the best way of sustaining the soil biological parameters and cycling of various important soil nutrients which may potentially alter vital soil processes resulting in increased agricultural sustainability.