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The relationship between pyroxasulfone bioactivity and soil properties has not been investigated in a wide range of soils typical of western Canada. In this study, 47 soils from Saskatchewan, Manitoba and Alberta, with varying organic matter content (1.5%–22.1%), pH (5.0–7.9), and clay content (6.8%–59.4%) were used to evaluate the effect of soil properties on pyroxasulfone bioactivity and its relevance to field application rates. Bioactivity was assessed by measuring the reduction of sugar beet shoot length after 7 days in response to 0, 92, 184, and 368 µg ai kg−1pyroxasulfone concentration in soil. Multiple regression analysis showed that pyroxasulfone bioactivity was related to soil organic matter content, pH and clay content. Grouping the soils according to these properties allowed for a summarization of pyroxasulfone field application rates required to achieve bioactivity based on the magnitude of sugar beet shoot length inhibition (%). The estimated field application rates ranged from less than 120–480 g ai ha−1. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]