Document Type

Article

Publication Date

9-2021

Keywords

Amaranth Amaranthus-palmeri; Auxin Herbicides; Glycine-max; Glyphosate; Injury; 2, 4-d; Drift; Rates

Abstract

Applications of dicambaherbicide to dicamba-resistant (DR) soybean [Glycine max (L.) Merr.] and cotton (Gossypium hirsutum L.) may increase the risks of non-DR soybean exposure to dicamba. Dicamba residue in sprayers poses a challenge for applicators that also treat non-DR soybean. Risks for non-DR soybean producers increase as the planted acreage and usage of DR crops increases, as there is potential for volatilization of the herbicide in the summer months, posing a risk for nearby non-DR soybean producers. There has been widespread speculation that a low-dose exposure of dicamba to sensitive soybean may elicit a positive response in yield or yield components of the crop. Therefore, experiments were conducted in 2018 and 2019 to assess the ability of dicamba to cause a hormetic response on a sensitive soybean. Dicamba at 0.000008, 0.0000125, 0.000025, 0.00005, and 0.0001 lb a.i. acre–1 was applied to soybean at the V3 stage along with a nontreated control. Similar treatments were applied to soybean at the R1 stage in a second experiment. In 2018, 4 out of 60 treatment means across six yield parameters had a positive response over the control, although no increase in yield was detected. In 2019, 11 out of 60 treatment means across the same yield parameters displayed a decrease and subsequently reduced soybean grain yield. The degree of auxin symptoms varied between site–years and did not consistently display compensatory effects. Overall, no findings led to the conclusion that exposure of soybean to sublethal doses of dicamba increased grain yield.

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