Adsorption and degradation studies of pretilachlor in three different soils of Punjab
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Date
2014
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Punjab Agricultural University, Ludhiana
Abstract
The present investigation was undertaken to study the adsorption-desorption and
degradation behaviour of pretilachlor in Punjab soils. Pretilachlor [2-chloro-2', 6'-diethyl-N-(2propoxyethyl)
acetanilide] is pre-emergence herbicide used for the control of sedges and
broadleaf weeds in transplanted and direct seeded paddy fields. Adsorption-desorption
experiments were carried out to study the effect of concentration, soil type and temperature, using
batch equilibration process. Pretilachlor was quantified using HPLC. The adsorption-desorption
data fitted well in Freundlich equation for three soils, irrespective of temperature. The adsorptiondesorption
of pretilachlor was in order: clay loam>sandy loam> loamy sand soil indicating
positive correlation of adsorption-desorption with organic matter and clay content. The values of
∆G were negative and increased with rise in temperature indicating that the adsorption-desorption
of pretilachlor on soil samples was a spontaneous endothermic process becoming more favourable
at higher temperature. Field trials were carried out to investigate the dissipation and residue levels
of pretilachlor in soil and water of paddy fields. Soil/rice samples were extracted using matrix
solid phase dispersion method and water samples were extracted using liquid-liquid extraction
technique. The dissipation of pretilachlor in paddy field soil and water followed first order
kinetics showing a half life of 7.52-09.58 days and 01.89- 02.97 days, respectively, at application
rate of 0.75 and 1.5 kg ha-1. Residues of pretilachlor at harvest in soil and rice grain were below
0.01 µg g-1.