Environmental Conditions, Variety, and Application Timing Influence on S-Metolachlor Sugarbeet Crop Safety
Abstract
Glyphosate-resistant weeds in North Dakota and Minnesota sugarbeet growing regions have necessitated research on S-metolachlor. S-metolachlor can be applied early-postemergence in sugarbeet but has not been labeled preemergence as reductions in sugarbeet safety have been observed. Field and growth chamber experiments were conducted to determine crop safety from S-metolachlor applied preemergence. S-metolachlor readily bonds to soil clay and organic matter. High clay and organic matter soils buffer S-metolachlor from soil solution and increase crop safety. Sugarbeet emergence was affected by soil series, temperature, and soil water, but was not affected by S-metolachlor or S-metolachlor rate. S-metolachlor affected sugarbeet growth, but a rate of 0.54 kg ai ha-1 was safe across soils and growing conditions. No differences in varietal tolerance were observed. S-metolachlor applied immediately after planting or at the cotyledon and two-leaf stage injured sugarbeet less than application 3, 5, or 7 d after planting.