Efficiency and Determination the Residue of Herbicides in Green Soybean Production

Abstract

  Studies on efficiency and determination the residue of herbicides in green soybean (Glycine max L. Merr. Variety No 75) production were carried out in the field experiment, Mae On subdistrict and the laboratory of Lanna Agro Industry Co., Ltd., Saraphi district, Chiang Mai province, in early rainy season during May, 2006 – July, 2008. Herbicides namely acetochlor, alachlor, clomazone, isoxaflutole, metribuzin, oxadiazon, pendimethalin, clomazone + pendimethalin and metribuzin+ pendimethalin were applied to evaluate the efficacy for weed control. All pre-emergence herbicides had variable weed controls in green soybean. Metribuzin, pendimetalin, and metribuzin+pendimethalin showed the best efficacy and no yield reduction. No visible crop injury was observed after alachlor, clomazone, metribuzin, pendimethalin, clomazone + pendimethalin and metribuzin + pendimethalin application, while acetochlor, isoxaflutole and oxadiazon caused visible crop injury to green soybean. The herbicide residues in crop yield were determined using Gas chromatography-Mass Spectrometry (GC-MS). No herbicide residues was detected in crop yield (or  MRLs < 0.01 ppm) for all herbicides used in the stydy. From these results, it was found that metribuzin at 84 g a.i./rai was sufficient to provide satisfactory full-season control of several weed species. In addition, pendimethalin at 165 g a.i./rai, and metribuzin at 56 g a.i./rai + pendimethalin at 148.5 g a.i./rai should be provided a similar level of weed control as an alternative to reduce herbicide dosage use, and further increased for the food safety in green soybean production.