Soybean growth and incidence of soil‐borne fungi as influenced by metribuzin

Abstract

AbstractSoybean injury following an application of metribuzin soon after planting can occur under cool, wet conditions, especially for varieties that lack a high level of tolerance to the herbicide. Field experiments were conducted in 2017 and 2018 in Fayetteville, AR, to evaluate the impacts of metribuzin at 0, 280, 560, 840, and 1,120 g ai ha−1 on soybean growth and incidence of soil‐borne fungi. Three classes of metribuzin tolerance (sensitive, moderately tolerant, and tolerant) were evaluated based on a previous screen. In both years, visible injury to soybean was impacted by varietal tolerance and metribuzin rate. As metribuzin rate and soybean sensitivity increased, more injury was observed. Metribuzin applied at 280, 840, and 1,120 g ha−1 in 2017 and only 1,120 g ha−1 in 2018 reduced soybean plant population, averaged across varieties, by 12, 23, 23, and 11%, respectively. Averaged over site years, metribuzin at 1,120 g ha−1 delayed the sensitive soybean cultivars from reaching 20, 40, 60, and 80% groundcover by 11, 12, 9, and 5 days, respectively, compared to the nontreated. Metribuzin‐moderately tolerant and metribuzin‐tolerant varieties did not suffer any delays in canopy formation. In both site years, the sensitive variety had a yield loss up to 21% following metribuzin at 1,120 g ha−1 when compared to the nontreated. Metribuzin did not impact colonization of soybean in either site year by microorganisms in the genus Acrophilaphora, Collectotrichum, Didymella, Fusarium, Pythium, Macrophomina, Phomopsis, Rhizoctonia, Rhizopus, and Trichoderma. Delays in canopy formation can be mitigated through appropriate variety selection.