The behavior of highly volatile pre-emergence herbicides in soil and their relative availability to plants under various conditions is poorly understood and pertinent information is much sought after by workers in chemical weed control. Ashton and Sheets reported an inverse relationship between injury to oats and soil adsorption of ethyl–N,N-di–n–propylthiolcarbamate (EPTC) in various soil types. Later, Sheets demonstrated a close relation between the initial toxicity of EPTC and soil types. EPTC was inactivated about one-third as rapidly in an autoclaved soil as in a corresponding unautoclaved one, from which he suggested that microbial breakdown may be a major pathway of EPTC inactivation when the chemical is incorporated in the soil.