Effect of soil type and organic manure on adsorption-desorption of flubendiamide.

Laboratory study on adsorption-desorption of flubendiamide was conducted in two soil types, varying in their physical and chemical properties, by batch equilibrium method. After 4 h of equilibrium time, adsorption of flubendiamide on soil matrix exhibited moderately low rate of accumulation with 4.52 ± 0.21% in red soil and low rate with 3.55 ± 0.21% in black soil. After amending soils with organic manure, adsorption percentage increased to 6.42 ± 0.21% in red soil and (4.18 ± 0.21%) in black soil indicating that amendment significantly increased sorption. Variation in sorption affinities of the soils as indicated by distribution coefficient (K d) for sorption was in the range of 2.98-4.32, 4.91-6.64, 1.04-1.45 and 1.92-2.81 ml/g for red soil, organic manure-treated red soil, black soil and organic manure-treated black soil, respectively. Desorption was slightly slower than adsorption indicating a hysteresis effect having hysteresis coefficient ranges between 0.023 and 0.149 in two test soils. The adsorption data for the insecticide fitted well the Freundlich equation. Results revealed that adsorption-desorption was influenced by soil types and showed that the maximum sorption and minimum desorption of the insecticide was observed in soils with higher organic carbon and clay content. It can be inferred that crystal lattice of the clay soil plays a significant role in flubendiamide adsorption and desorption. Adsorption was lower at acidic pH and gradually increased towards alkaline pH. As this insecticide is poorly sorbed in the two Indian soil types, there may be a possibility of their leaching to lower soil profiles.