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bioweb.sungrant.org » Technical » Biomass Resources » Agricultural Resources » New Crops » Herbaceous Crops » Switchgrass

Switchgrass	Printer Friendly

Switchgrass (Panicum virgatum) is a warm season perennial whose native range includes all of the U.S. east of the Rocky Mountains and extends into Canada and Mexico. It is a major species of the prairies that covered much of the American heartland prior to the introduction of agriculture. Switchgrass is a C4 species (i.e., the first product of photosynthesis is a four carbon compound), consists of numerous upland and lowland varieties, and displays substantial genetic diversity. Switchgrass has been produced as a forage crop and used for conservation purposes for many years, but its development as a potential energy crop began in 1991 as part of the U.S. Department of Energy’s Biomass Feedstock Development Program at Oak Ridge National Laboratory. Field trials were  established at 18 sites (13 states including VA, WV, TN, KY, NC, GA, AL, TX, AR, LA, ND, SD, and IA) and evaluated 9 cultivars to identify best regional varieties, establish appropriate management practices, and conduct genetic research to improve yield and performance characteristics. The Alamo variety was determined to be the best cultivar tested for production in the South, Alamo and Kanlow best for mid-latitude production, and Cave-in-Rock, Trailblazer, and Sunburst varieties best suited for northern latitudes.   Under research conditions (5-10 years data; one cut production system, multiple sites and states), yields of Alamo and Kanlow averaged 12 to 19 Mg/ha/year (5.35 to 8.45 dry ton/acre/year) and 11.6 to 15.5 Mg/ha/yr (5.2 to 6.9 dry tons/acre/year) respectively.  The best one year yield attained under a two cut system was for Alamo in Alabama (34.6 Mg/ha; 15.4 dry tons/acre). Both Alamo and Kanlow varieties produce high yields in the South (except for arid conditions in TX) under a one and two cut system and maintain high yields for a number of years, however, two cut systems are more intense and require greater energy and nutrient inputs than single cut systems. The oldest continuous research plot for Alamo was established at Auburn University in 1988 and has averaged 23 Mg/ha (about 10 dry tons/acre) over a 13 year time period. First generation synthetic cultivars (hybrids) are yielding up to 30 percent higher yields than their parent lines, but are still being evaluated and are not commercially available.   Switchgrass is a perennial and needs planting only once during a multi-year period. Generally, a ten year production rotation is assumed before replanting, but periods of different lengths are possible if circumstances warrant it. Switchgrass has a deep root system—the below ground biomass is as great as the above ground biomass. This large and deep root system, combined with fine root turnover, makes switchgrass an excellent crop for erosion control and to add organic matter to depleted soils.     Switchgrass is produced using standard agricultural equipment. It requires a firm seedbed and a shallow planting depth making it appropriate for no-till planting. Seed density must be sufficient to provide a good stand (2 plants/ft2; 7-8 pounds pure live seed/acre).  Weed control is required in the establishment (first) year and usually consists of one pre-emergent herbicide application and 1 to 2 post-emergent applications. Herbicides are generally not required after the establishment year. At the current time, few herbicides are labeled for use on switchgrass--more are needed.   Switchgrass is nutrient and water efficient and requires no fertilizers in the establishment year. Nitrogen is applied annually in subsequent years at recommended rates of 50 lbs N/acre for most regions (up to twice this level under some circumstances such as in the South Plains where little nitrogen is available from natural sources). Phosphorus and potassium are added only if soil tests indicate low levels. Recommended rates are around 15-20 lb P/acre and 25 lb K/acre. Switchgrass tolerates acid and alkaline soils within a range of pH 5-8 and under typical production conditions will not require lime. These recommended rates are appropriate for production systems consisting of one harvest per year following senescence which allows nutrients to be translocated to the roots for use in the following growing period. Production systems involving more than one harvest per year, including harvest during the active growing period, require higher levels of nutrients. Switchgrass resists lodging, and can be harvested anytime after senescence and before shoot emergence the next spring if the ground is sufficiently dry to permit harvest. Research in Alabama has shown that a single harvest in late August or early September allows for the development of a short canopy in the fall that reduces competition from winter weeds, protects spring shoots from late frosts, and provides excellent wildlife habitat over winter.   Switchgrass typically takes three years to reach its full mature yield although harvest can still be conducted in the first two years.  Yields in the first (establishment) year are typically 20 to 35 percent of mature yields and in the second year are typically 60 to 75 percent of mature yields. Switchgrass can be produced throughout the U.S., but research and development efforts have mostly been limited to areas east of the Rocky Mountains. Expected yields and estimated production costs vary substantially by region.   Switchgrass is not currently produced as a bioenergy crop in the U.S. and large scale production for this use will require it to compete with existing uses for agricultural land. A recent U.S. DOE study estimated that by mid-century, 163 million dry tons of switchgrass could potentially be available on non-Conservation Reserve cropland acres based on an assumed removal rate of 4.2 dry ton/ac on 35 million acres of cropland drawn primarily from pasture, hay, and fallow acres. Under a high crop yield scenario, the study estimates that 368 million dry tons could be available assuming removable yields of 6.7 dt/ac and 55 million acres of production with acres coming mostly from pasture, hay, fallow, wheat and soybean acres. No economic analysis was conducted.   A recent economic study that examined the commercial potential to produce switchgrass throughout the U.S. estimated that 293 million dry tons of switchgrass could potentially be supplied at a price of $50/dry ton or less by the year 2025 (table 1).                   The study used a dynamic model of the U.S. agricultural sector (POLYSYS) that shifts cropland acres from current uses to switchgrass production based on relative profits. The analysis assumed expected 2005 regional harvest yields (cropland acres, rainfed conditions) ranging from about 2 to 6.5 dry tons/acre (figure 1).            Yield increases ranging from 20 to 60 percent (depending on region) were assumed between 2005 and 2025. Estimated current regional production costs ($2002/dry ton) used in the analysis are shown in figure 2.            Estimated costs range from less than $25/dry ton to nearly $90/dry ton depending on region. Production costs are estimated as net present costs over the entire rotation using American Agricultural Economics Association recommended methodology and include the costs of seed, fertilizer, herbicide, operating interest, producer’s own labor, and the costs associated with owning and operating equipment (fuel, oil, and lubrication; depreciation and interest; repairs; and insurance, taxes, and housing). Harvest assumes mowing, raking, baling (large round bales), and moving the bales to the edge of field and stacking. The estimated costs include regional variation in input prices. Establishment and fertilizer costs remain unchanged throughout the period of the analysis, but it assumed that new harvesting methods will be developed which will reduce harvest costs over time (a maximum reduction of 25 percent by 2025). Figure 3 shows the regions where switchgrass production is most competitive with existing land uses for the year 2015 and assuming a crop price of $40/dry ton. Switchgrass is most competitive with existing land uses in the southeastern and northeastern U.S. and in a ring surrounding the Corn Belt.

Sources
De La Torre Ugarte, Daniel G., Marie E. Walsh, Hosein Shapouri, and Stephen P. Slinsky, The Economic Impacts of Bioenergy Crop Production on U.S. Agriculture, U.S. Department of Agriculture, Agricultural Economic Report Number 816, February 2003. McLaughlin, Samuel B. and Lynn Adams Kszos, Summary of 10 Years of Research Progress in Improvement of Switchgrass (Panicum virgatum) as a Dedicated Bioenergy Feedstock, Oak Ridge National Laboratory, Draft Manuscript, 2005. Ocumpaugh, W., M. Hussey, J. Read, J. Muir, F. Hons, G. Evers, K. Cassida, B. Venuto, J. Grichar, and C. Tischler, Evaluation of Switchgrass Cultivars and Cultural Methods for Biomass Production in the South Central U.S.—Consolidated Report 2002, Oak Ridge National Laboratory, ORNL/SUB-03-19XSY091C/01, May 2003. Parrish, D.J., D.D. Wolf, J.H. Fike, W.L. Daniels, Switchgrass as a Biofuels Crop for the Upper Southeast: Variety Trials and Cultural Improvements—Final Report for 1997 to 2001, Oak Ridge National Laboratory, ORNL/SUB-03-19XSY163/01, May 2003. Taliaferro, Charles M., Breeding and Selection of New Switchgrass Varieties for Increased Biomass Production, Oak Ridge National Laboratory, ORNL/SUB-02-19XSY162C/01, December 2002. Taliaferro, C.M, K.P. Vogel, and J.H. Bouton, Scale-Up and Commercialization of New Switchgrass Cultivars, Oak Ridge National Laboratory, March 2000. U.S. Department of Agriculture, Agricultural Research Service, Bioenergy and Energy Alternatives National Program, www.ars.usda.gov.proxy.lib.utk.edu:90/research/programs/programs.htm?np_code=307&d. Vogel, K.P. and H.G. Jung, Genetic Improvement of Switchgrass and Other Herbaceous Plants for Use as a Biomass Fuel Feedstock—Final Report, Oak Ridge National Laboratory, ORNL/SUB/90-90OR21954/1, September 2000. Walsh, Marie E., Daniel G. de la Torre Ugarte, Hosein Shapouri, and Stephen P. Slinsky, Bioenergy Crop Production in the United States--Potential Quantities, Land Use Changes, and Economic Impacts on the Agricultural Sector, Environmental and Resource Economics, vol. 24, pp. 313-333, 2003. S. McLaughlin, J. Bouton, D. Bransby, B. Conger, W. Ocumpaugh, D. Parrish, C. Taliaferro, K. Vogel, and S. Wullschleger, 1999, Developing Switchgrass as a bioenergy crop, In: Perspectives on new crops and new uses, J. Janick (ed.), ASHS Press, Alexandria, VA, pp. 282-299. Mike Duffy and Virginie Y. Nanhou, 2001, Costs of producing switchgrass for biomass in Southern Iowa, Iowa State University, PM 1866. D.W. Meyer, W.E. Norby, D.O. Erickson, and R.G. Johnson, 1994, Evaluation of herbaceous biomass crops in the northern Great Plains--final report, Oak Ridge National Laboratory, ORNL/Sub/88-SB844/2 Marie E. Walsh, 2006, U.S. cellulosic biomass feedstock supplies and distribution (revised), Farm Foundation Conference--Energy from Agriculture: New Technologies, Innovative Programs, and Success Stories, St. Louis, MO, December 14-15, 2005. Robert D. Perlack, Lynn L. Wright, Anthony F. Turhollow, Robin L. Graham, Bryce J. Stokes, and Donald C. Erbach, April 2005, Biomass as feedstock for a bioenergy and bioproducts industry: the technical feasibility of a billion-ton annual supply, Oak Ridge National Laboratory, ORNL/TM-2005-66. Marie E. Walsh, November 2006, Estimated U.S. Switchgrass Supply—Documentation of Methodology, Unpublished Manuscript.