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The Center for Native Grasslands Management

Title: Seed safening for use in switchgrass establishment
Year: 2010
Author(s): Rushing, B., Baldwin, B., Taylor, A.
Source Title:
Source Type: Proceedings
pages: 65
Original Publication:  
Abstract: Switchgrass (Panicum virgatum) is a native warm season grass that is considered to be in the forefront of biomass-to-fuel production. The major limiting factor in the establishment of switchgrass is annual grassy weed control. The objective of this research is to test the seed safener, fluxofenin at four rates and two treatment methods. Determining the optimal rate and seed application method would provide distinct advantages in switchgrass establishment and weed control, potentially enabling fertilization and significantly increasing production during the establishment year. Fluxofenin, the active ingredient in the commercial safener Concep III, safens seed against the herbicide metolachlor. Preliminary testing of nine safeneners indicated that fluxofenin, applied at a quarter the labeled rate for sweet sorghum (Sorghum bicolor) (0.4 g a.i./kg of seed), protected switchgrass seedlings from herbicidal injury, while providing excellent weed control. Subsequent testing of safener coating methods (seed soak vs. brushing), rates (full rate, half rate, quarter rate), and eleven switchgrass varieties (lowland and upland) was conducted in the summer of 2010 at four sites: Mississippi State, Iowa State, Virginia Tech, and South Dakota State University. Nine treatments were planted on 3 m (10 ft) rows with 50 cm (20 in) spacing in four replications. All varieties were tested for germination pre-coating and were planted at a 9 kg PLS/ha (8 lb PLS/A) seed rate. Metolachlor was applied in the form of Dual Magnum at a rate of 0.91 kg a.i./L (1.17 L/ha or 1.0 pt/A) immediately following planting. Seedling counts were conducted four weeks after planting and there were no significant differences between the control (no safener/no herbicide; 4.92 seedlings per 15 cm) and the quarter rate of safener (4.37 seedlings per 15 cm). There were no significant differences in weed control ratings between treatments, however there were differences between weeks; as season progressed, weed pressure increased. End of season harvest results show the quarter rate of safener with the variety ‘Alamo’ and the control were significantly higher in tonnage than all other switchgrass varieties and treatments with 3.45 Mg/ha (1.20 ton/A) and 2.14 Mg/ha (0.96 ton/A), respectively. In conclusion, ease of establishment along with establishment year fertilization can be achieved through the use of the safener Concep IIII and the pre-emerge herbicide Dual Magnum.
Publisher: Proceedings of the Seventh Eastern Native Grass Symposium. Knoxville, TN, October 5-8, 2010
Editor(s): C. Harper