ARS | Publication request: Growth of switchgrass as biofuel in the Pacific Northwest

Submitted to: Eastern Native Grass Symposium
Publication Type: Proceedings
Publication Acceptance Date: October 10, 2006
Publication Date: October 10, 2006
Citation: Steve Fransen, Harold P. Collins and Rick A. Boydston. 2006. Growth of switchgrass as biofuel in the Pacific Northwest. Pp 2-3. Proceedings of the 5th Eastern Native Grass Symposium, Harrisburg, PA October 10-13, 2006.

Technical Abstract: Switchgrass (Panicum virgatum) has been grown as a seed crop in the Pacific Northwest (PNW) for more than 20 years but monitoring for adaptability as forage or research into biomass for ethanol production had been lacking until about five years ago. During the past five years we have established eight field research studies at two irrigated field sites at Paterson, WA and Prosser, WA to evaluate switchgrass production potentials in the PNW. Varieties evaluated include Alamo, Kanlow, Dacotah, Cave-In-Rock, Trailblazer, Blackwell, Nebraska 28, Sunburst, Forestburg and Shawnee. Switchgrass seed is naked, very small with about 325,000 to nearly 400,000 easy to drill seeds per pound. When planting maintain a clean and firm seedbed using covering chains or packing wheels to ensure good soil-seed contact for rapid germination. We have successfully established stands with seeding rates ranging from 7 to 12 pounds per acre with a drill on 6-inch centers. Seed germination for different varieties has ranged from less than 30 to more than 70%, so it is important to check germination rate and adjust planting equipment appropriately. Weed control is a major issue during the first-year establishment period. Several herbicide trials at Paterson showed Prowl (pendimethalin) applied pre or post-emergence at 0.66 to 1 pound ai/ac provided excellent control for many of our problem weeds at both locations. However, Prowl applied to sandy soils at Paterson nearly destroyed the establishing switchgrass stands. With a loamy soil at Prosser, Prowl used pre-emergence caused stunting during early seedling establishment but lessened as seedling plants developed. Prowl does not provide season long control because of seasonal irrigation that stimulates the weed seedbank. We have found injury differences among switchgrass varieties for post-emergence products. Callisto (mesotrione) damaged both Cave-In-Rock and Shawnee varieties more than Kanlow. Dacotah is the earliest maturing and may be too early for biofuel production in the lower Columbia Basin region. We believe Dacotah maybe best adapted to a higher elevation, shorter growing season where natural precipitation is adequate for this deeply rooted plant to survive. Over fertilization of switchgrass stimulates weed growth where the grass produces well with minimum level of soil nutrition. For biofuel production we harvest 2 times per growing season. The first harvest occurs in early to mid-July and second at the end of the season in late September or early October. Adequate stubble height is essential to sustain the crop. As a biomass managed crop for ethanol production and maintenance of adequate stubble, long-term survival should likely not be an issue. Switchgrass is a viable crop in the warm regions of the PNW if natural rainfall is adequate or irrigation water is applied.