A bioassay evaluation of pyroxasulfone behavior in prairie soils

Abstract

Pyroxasulfone behavior in prairie soils was evaluated using a 7-day sugar beet (Beta vulgaris L.) shoot length inhibition bioassay. Pyroxasulfone bioactivity in soil, assessed from 0 to 184 g a.i./kg, was primarily related to organic carbon content (p=0.001) with decreased bioactivity occurring in soils of high organic carbon. Pyroxasulfone bioactivity, measured after soil pH adjustments, was reduced as soil pH decreased demonstrating that at low soil pH pyroxasulfone becomes less available to plants. Pyroxasulfone half-lives estimated for dissipation at 25°C and moisture content of 85% field capacity ranged from 16 to 69 days. Organic carbon content (p=0.034) and soil pH (p=0.008) were significant in affecting pyroxasulfone half-lives with faster dissipation occurring in soils of high organic carbon content and high pH. Interactions between soil-incorporated pyroxasulfone and sulfentrazone were either antagonistic or additive and the nature of these interactions could vary with soil type. © Pesticide Science Society of Japan.