Polyethylene (PE) film formulation incorporated with herbicide metolachlor for controlled release

Modern agricultural practices for some cash crops in the Republic of Korea accompany with plastic sheet mulching to keep soil moisture, to elevate soil temperature and to increase crop productivity. PE film formulation incorporated with metolachlor was investigated as a controlled-release pesticide to eliminate an operation for pesticide application. An uniform film was able to be formulated by thermal extrusion of low density polyethylene (LDPE) or LDPE and ethylene vinyl acetate (EVA). The physical properties of the films met domestic industrial standards of PE, even with little lower values in tensile, elongation and tear strength than LDPE alone. Incorporated rate of metolachlor into the film amended with EVA was to some extent higher than those with LPDE alone. On the other hand, release profile of the chemical from the film prepared by LDPE and EVA into water systems showed a little slower than that prepared by LDPE alone. Metolachlor residue in the top soil of red pepper field mulched the films was maintained around one ppm up to 90 days after application. Weed control effect of the films on key annual weeds in the field was equivalent to conventional practices; spraying metolachlor EC followed by mulching PE film. No phytotoxicity was observed during the whole growth period of the crop. Retained amount of metolachlor in the films after crop harvest, 90 days after mulching, was 0.28ug to 0.3ug per sq. cm., which was equal to 1.6% to 1.7% of the original amount. (author). 9 refs, 5 figs, 5 tabs