Degradation of Triazine-2-14C Metsulfuron–Methyl in Soil from an Oil Palm Plantation

Abstract

Triazine-2-14C metsulfuron–methyl is a selective, systemic sulfonylurea herbicide. Degradation studies in soils are essential for the evaluation of the persistence of pesticides and their breakdown products. The purpose of the present study was to investigate the degradation of triazine-2-14C metsulfuron–methyl in soil under laboratory conditions. A High Performance Liquid Chromatograph (HPLC) equipped with an UV detector and an on-line radio-chemical detector, plus a Supelco Discovery column (250 x 4.6 mm, 5 μm), and PRP–1 column (305 x 7.0 mm, 10 μm) was used for the HPLC analysis. The radioactivity was determined by a Liquid Scintillation Counter (LSC) in scintillation fluid. The soil used was both sterilized and non-sterilized in order to observe the involvement of soil microbes. The estimated DT50 and DT90 values of metsulfuron-methyl in a non-sterile system were observed to be 13 and 44 days, whereas in sterilized soil, the DT50 and DT90 were 31 and 70 days, respectively. The principal degradation product after 60 days was CO2. The higher cumulative amount of 14CO2 in 14C- triazine in the non-sterilized soil compared to that in the sterile system suggests that biological degradation by soil micro-organisms significantly contributes to the dissipation of the compound. The major routes of degradation were O-demethylation, sulfonylurea bridge cleavage and the triazine “ring-opened.”

Residue and Dissipation Kinetics of Metsulfuron-Methyl Herbicide in Soil: A Field Assessment at an Oil Palm Plantation

“…Half-lives of 6.3 and 7.9 days were estimated from the first-order kinetics of the degradation process for both application rates ( Table 4 ). Dissipation of 14 C-phenyl metsulfuron-methyl and 14 C-triazine metsulfuron-methyl was also found, and followed the first-order kinetics model from our earlier study [ 5 , 25 ]. A similar observation was reported by Ismail and Chong [ 4 ], where the half-lives of metsulfuron-methyl in an oil palm field ranged from 7.4 to 9.2 days and 8.2 to 13.4 days when the herbicide was applied at 15 and 30 g a.i/ha, respectively.…”

“…The high microbial activity in the oil palm ecosystem might also enhance the degradation of metsulfuron-methyl in the soil. A previous study showed that the DT50 (the time required for 50% of the applied chemical to degrade) values of 14C-phenyl metsulfuron-methyl and 14C-triazine metsulfuron-methyl were 12 days and 14 days, respectively, in non-sterile soil, and 19 days and 23 days in sterile soil [ 5 , 25 ]. These results indicate that degradation of metsulfuron-methyl in the soil is caused by both chemical and microbial processes by soil microorganisms.…”

“…Previously, there h been a number of studies on the persistence, mobility, and bioactivity of metsulfuron-methyl conducted in Malaysian agricultural soils [ 4 , 24 , 25 ]. However, the information obtained did not resemble the actual situation and variables in the environmental factors involved.…”

Epinastic Growth and Accordion-Type Leaf Formation of a Phoenix Canariensis Following Herbicide Application

“…Broschat (1986, 1987) noted that direct application of glyphosate led to leaf distortion on several species of palms, but that this effect was not long-lasting at the concentrations were tested. Various studies consider the impact of Metsulfuron-Methyl herbicides on the soil of oil palm plantations (Ismail et al, 2015;Zain et al, 2013), but as in the case of glyphosate herbicides, none of the studies have examined the impact of direct application of the herbicide on the palm itself. Metsulfuron-Methyl inhibits cell division in shoots (Bayer, 2015), which may well manifest itself in the leaf malformation.…”