Effect of Safener, Activated-charcoal Coated Seed, and Charcoal Banding on Establishment of Switchgrass Receiving Pre-emergent Herbicides

Abstract

Switchgrass (Panicum virgatum L.) is typically slow and difficult to establish due to competition from weeds. Two experiments were conducted evaluating effectiveness of seed safeners and activated charcoal on prevention of herbicide injury of ‘Alamo’ switchgrass. In experiment I, a completely randomized greenhouse experiment with three replications evaluated a factorial arrangement of five (0, 0.64, 0.96, 1.28, and 1.92 fluid oz/100 lb seed) fluxofenin (Concep III) rates and four herbicide treatments: metolachlor, metolachlor plus atrazine, pendamethalin, and an untreated control. In experiment II, a randomized complete block field experiment with a split plot arrangement of treatments and four replications evaluated charcoal seed treatments. Main plot treatments consisted of uncoated seed plus 250 lb/acre charcoal slurry in a 2-inch band over the seed row, charcoal coated seed at either 4:1, 6:1, or 8:1 charcoal weight:seed weight ratios, and non-treated seed. Sub-plot treatments consisted of five herbicide treatments: atrazine, metolachlor, metolachlor plus atrazine, imazapic, and an untreated control. In experiment I, fluxofenin did not safen switchgrass seeds from these herbicides. In experiment II, charcoal treatments safened switchgrass seed in 2 of 4 years, when precipitation was above normal, but failed to safen switchgrass seed when rainfall was below average. In addition, switchgrass ground cover at end of season was generally below the minimum 40% threshold; therefore improved establishment techniques are still needed for switchgrass.