Persistence and efficacy of flumioxazin as affected by soil organic matter, clay content and soil pH.

Calvin Glaspie, Wesley Everman, Andrew Chomas
Michigan State University, East Lansing, Michigan, USA


Previous studies have been conducted on the persistence of flumioxazin to understand its environmental fate in the soil. These studies however, have not focused on the impact soil constituents have on flumioxazin's residual weed control. To understand the effect soil amendments and pH have on residual weed control of flumioxazin, a replicated greenhouse experiment was conducted in 2008 and 2009 at Michigan State University. The statistical design was a factorial arrangement of treatments with soil amendment percentage factored by herbicide treatment being non-treated or treated with 70.62 g ai/ha of flumioxazin. Clay soils used in the study ranged from 0-70% by mass and were created by adding kaolin clay to construction sand. Organic soils used in the study ranged from 0-32% organic matter by mass created by adding muck soil (88% organic material) to construction sand. Soils with varying pHs were created by acidifying (H3PO4) or neutralizing (NaOH) a control soil (pH of 4.56) to Phs ranging from 4-9. 100 weed seeds of 5 different weed species were incorporated into the top 1.27 cm of each soil. Emerged plants were counted and removed in both treated and not-treated pots 2 weeks after planting, and each following week for 6 weeks. Efficacy of flumioxazin was evaluated by calculating percent emergence of weeds in treated soils compared to emergence of weeds in non-treated soils. Efficacy of flumioxazin was not affected by clay content or soil pH, but decreased as organic matter content increased however additional work is still needed.