Influence of soil factors on the dissipation of a new pyrimidynyloxybenzoic herbicide ZJ0273.

A novel pyrimidynyloxybenzoic herbicide (ZJ0273) uniformly labeled with (14)C on the benzoate ring was applied to soils under sterile and nonsterile conditions to understand the effect of soil microorganisms and selected properties on its dissipation and transformations to bound resides and (14)CO(2). A significant effect of soil microorganisms was found in an acidic soil, where sterilization significantly prolonged the half-dissipation time (DT(50)) of ZJ0273 from 15.57 to 34.31 days and decreased the total amount of mineralized (14)CO(2) from 19.91 to 0.43%. However, sterilization showed limited effect on the patterns of bound residue or extractable residue levels in soils having pH > or = 6.1. In addition, a significant suppression of high pH was found on the dissipation of extractable residues and formation of bound residues. The enhancement of bound residue formation by low soil pH was attributed to increased conversion of ZJ0273 to its intermediates, which were rapidly bound to soil organic matter.

Bound 14C-metsulfuron-methyl residue in soils.

Bound residue(BR) of 14C-metsulfuron-methyl (14C-BR) in seven kinds of soil was significantly negative-related to soil pH and positive-related to the clay content during the initial 20 d of incubation, but only was significantly negative-related to soil pH after 30 d incubation. Again, the soil pH was found to be the dominant factor affecting BR formation from 14C-metsulfuron-methyl among the basic properties(soil pH, clay, OM and CEC etc.) of soil. The maximum content of 14C-BR in the 7 soils accounted for 19.3% - 52.6% of applied amount. In addition, the composition of the 14C-BR in fluvio marine yellow loamy (S7) at the 90 d of incubation was identified using the coupling technique of LC-MS and isotope tracing method. The results showed that the 14C-[2-amino-4-hydroxyl-6-methyl-1, 3, 5]-triazine, 14C-[2-amino-4-methoxy-6-methyl-1, 3, 5]-triazine and 14 C-metsulfuron-methyl parent compound constituted the main components of the BR derived from 14 C-metsulfuron-methyl in the S7. The relative percentage of the three compounds accounted for 41.4%, 35.8% and 19.3% of total recovery radioactivity, respectively. The results also indicated that a non-radioactive component, 2-methylformate-benzenesulfonyl-isocyanate, one of the degraded products of metsulfuron-methyl in soil, was also found to be one of the components of the BR. The parent compound in BR can well explain the phytotoxic effect on substitution crops caused by the BR derived from metsulfuron-methyl in soil.