Adsorption, desorption and mobility of amide herbicides in four soil series
1991
Ubonvan Keittibunyarit
In laboratory experiments, Freundlich adsorption isotherms and distribution coefficient exhibited that amides were adsorbed in the order napropamidepretilachlormetolachlordiphenamid. Rf values indicated that the order of herbicide movement to be pretilachlordiphenamidmetolachlornapropamide. However every high rate of pretilachlor movement was occurred only in Bangkhen clay and Sattahip loamy sand. Furthermore, very small fraction of pretilachlor mobilied but the large fraction remained at the site of application. All herbicides were desorbed in all soil types. It was demonstrated that diphenamid and metolachlor were sufficiently mobile in soils of low organic matter and clay contents and caused possible loss of efficacy or accumulated in ground water. Greenhouse experiments and field experiments indicated that amides were more effective on grass (Dactyloctenium aegyptium (Linn.) Beauv.) than dicotyledon weed (Amaranthus viridis Linn.) except metolachlor which was effective on both Dactyloctenium aegyptium (Linn.) Beauv. and Amaranthus viridis Linn. The rates of four herbicides required for 80 % weed control in three soil series except Bangkhen clay loam were in the order Pakchong clay loamKampangsaen loamSattahip loamySattahip loamy sand in greenhouses and field experiments that are similar to the results from laboratory experiments. Herbicides are adsorbed by the soil with higher organic matter and clay more than by the soil with low organic matter and clay. High rate of herbicides must be applied in soil with high organic matter and clay.
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