Quinalphos Behaviour In Tea Soil

Quinalphos is a broad-spectrum organophosphorus insecticide and acaricide with good penetrative properties. Because of its broad spectrum application in tea plantation there has been growing concern among the regulation agencies, researcher and environmentalists to know its fate in tea and the surrounding environment. A study was undertaken to evaluate the degradation behavior of quinalphos in tea soil. The pesticide was applied at the doses recommended by the manufacturers (400 gm a.i./ha) and at double the recommended dose (800 gm a.i./ha). Soil samples were periodically collected upto 21^st days after spray and extracted using dichloromethane as solvent. A parallel study was carried out in laboratory-controlled conditions to study the effect of soil pH at three different temperatures (25, 50 and 75°C) and for that, field soil samples were prepared at different pH. The results revealed that quinalphos dissipation followed first order reaction rate ranging between 1.28–4.95 days. The dissipation was faster in wet season since in dry season soil drying tends to promote the adsorption of quinalphos in the soil matrix, thus limiting its availability for transport to the soil surface. The laboratory studies indicated that the quinalphos was susceptible to acid hydrolysis but stable under mildly basic conditions.