Residual effect of combi formulation of hexythiazox and diafenthiuron on soil enzymatic activity

Soil enzymes serve as efficient bioindicators of soil health and very sensitive to agricultural practices, climate, pH and nutrients. To assess the impact of combi formulation of hexythiazox + diafenthiuron on soil enzymatic activity, an experiment was conducted on chilli at Dr. Rajendra Prasad Central Agricultural University, Pusa during the summer season of 2023. The combi formulation of Hexythiazox 3.5% + Diafenthiuron 42% WDG was applied three times at their recommended dose (295.75 g a.i. per ha), 1.5 times of the recommended dose (443.62 g a.i. per ha), and twice of the recommended dose (591.50 g a.i. per ha) to manage chilli yellow mite. The results indicated that Hexythiazox + Diafenthiuron had deleterious effect on dehydrogenase and phosphatase activity at all doses; however, enzyme activity was recovered after 10th day onwards. Higher enzymatic activities were recorded in untreated control soil. The GMean index also exhibited similar trends, indicating a negative influence of combi formulation on soil biochemical processes. A significant decline in this index was observed in treated soil compared to the control for both enzymatic activities. This study makes an effort to extend this index's use beyond its current application.