Vertical migration of some herbicides through undisturbed and homogenized soil columns.

A laboratory experiment was conducted by using three herbicides, two from dinitroaniline group and one from thiocarbamate group to know their degree of downward movement (leachability) through soil columns and their contribution in ground water contamination. Soil columns were loaded with Pendimethalin, Benthiocarb and Oryzalin at doses of 10.0, 10.0 and 7.7 kg/ha, respectively. After 30 days soil samples were analyzed from each segments (i.e. 0-6, 6-12, 12-18, 18-24 and 24-30 cm) for Benthiocarb and Pendimethalin by GLC equipped with Ni(63) electron capture detector (ECD) and for Oryzalin by HPLC coupled with UV-VIS detector. The results obtained in the present study reveal that the residues of the three herbicides under investigation were predominantly confined to the upper soil layer (0-6 cm). Comparatively, low mobility of these herbicides in soils could be due to strong adsorption of these chemical to soil colloids.