Modeling Vapor Losses of Soil‐Incorporated Triallate

Vapor losses of triallate [S‐(2,3,3‐trichloroallyl) diisopropylthiocarbamate] incorporated into two soils with widely different organic matter contents were measured in the absence and presence of evaporating water. Adsorption isotherms (relating triallate solution concentrations to adsorbed triallate) were used to compare predicted and measured transport of triallate by mass flow and diffusion. With San Joaquin sandy loam, volatilization rate was greater when water was evaporating than when evaporation was suppressed but with Flanagan silt loam packed to a much lower bulk density, vapor loss was nearly the same in the presence and absence of evaporation. Total vapor losses during the 29‐ or 30‐day, period were 2.97 and 3.76% of the amounts applied from San Joaquin sandy loam and 3.72 and 3.80% from Flanagan silt loam without and with evaporation, respectively. Good agreement was observed between the total measured triallate vapor flux with evaporation and the convective mass flux calculated from the product of the solution concentration below the surface times the water evaporation flux.