Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/16/1998
Publication Date: N/A
Citation: Interpretive Summary: Triadimefon is a systemic fungicide with protective, curative and eradicant action. It is used as a foliage fungicide and as a soil fungicide in control of powdery mildews in cereals, vegetables, and fruits and in many diseases of turf. Little information has been published on the fate of triadimefon in soil, and data concerning the sorption behavior of triadimefon in soil are particularly scarce. Sorption is a major process determining the fate of pesticides in soil because it determines the amount of agrochemical in solution, and consequently the amount that can reach the target organism and that is susceptible to leaching, volatilization, and decomposition. We found that soil organic matter and clay are active in sorption of triadimefon. In soils with medium to high organic matter and clay contents, triadimefon would have an extremely low potential to leach through soil. We also found that as the concentration decreases, sorption increases, thereby further minimizing the potential to leach, even in soil with low organic matter and clay contents. This information is important to farmers, regulatory agencies, and the public to show that correct use of triadimefon to control diseases would not be a threat to leach through soil to ground water.
Technical Abstract: Sorption-desorption of the azole fungicide triadimefon [1-(4-chlorophenoxy)-3,3-dimethyl-1H-(1,2,4-triazol-1-yl)butan-2-one] on three soils and a series of single, binary, and ternary model soil colloids was determined using the batch equilibration technique. Calculated slopes of the Freundlich sorption isotherms were very similar for all three soils and significantly less than 1, indicating a limited number of sorption sites is available. Freundlich sorption constants, Kf, normalized to the organic C content of the soils suggesting that mineral constituents at low organic C contents and/or the type of organic matter may be important in determining triadimefon sorption by soils. Triadimefon distribution coefficients on soil were little affected by the concentration of electrolite or the presence of soluble soil material in solution, but they were highly dependent on the soil:solution ratio, due to the nonlinearity of triadimefon sorption on soil. Desorption did not depend on the concentration at which it was determined and showed hysteresis only for the two soils with the highest organic matter contents. Results of triadimefon sorption on single model soil constituents indicated that humic acid is the most important single soil constituent in triadimefon sorption; however, sorption on montmorillonite-type mineral can be very high, especially at high fungicide concentrations and low pH values.