Panicum virgatum

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Switchgrass
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Switchgrass

Secure  (NatureServe)[1]
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Clade: Commelinids
Order: Poales
Family: Poaceae
Subfamily: Panicoideae
Genus: Panicum
Species:
P. virgatum
Binomial name
Panicum virgatum

Panicum virgatum, commonly known as switchgrass, is a

biosequestration of atmospheric carbon dioxide, and more recently as a biomass crop for ethanol and butanol
.

Other common names for switchgrass include tall panic grass, Wobsqua grass, blackbent, tall prairiegrass, wild redtop, thatchgrass, and Virginia switchgrass.

Description

Switchgrass is a hardy, deep-rooted,

chemical fertilizers.[3]
Overall, it is considered a resource-efficient, low-input crop for producing bioenergy from farmland.

  • Root system of switchgrass grown at the Land Institute
    Root system of switchgrass grown at the
    Land Institute
  • Seeds, Kirt Prairie
    Seeds, Kirt Prairie

Habitat

Much of North America, especially the prairies of the Midwestern United States, was once prime habitat to vast swaths of native grasses, including switchgrass,

orchardgrass[5] also replaced the native grasses for use as hay and pasture for cattle.[4]

Distribution

Panicum virgatum ecotypes and their distribution in the United States of America[6]

Switchgrass is a versatile and adaptable plant. It can grow and even thrive in many weather conditions, lengths of growing seasons, soil types, and land conditions. Its distribution spans south of latitude 55°N from

Gulf Coast area.[8]

Switchgrass is a diverse species, with striking differences between plants. This diversity, which presumably reflects evolution and adaptation to new environments as the species spread across the continent, provides a range of valuable traits for breeding programs. Switchgrass has two distinct forms, or "cytotypes": the lowland

bunchgrass habit, while the upland types tend to be more sod-forming. Lowland cultivars appear more plastic in their morphology, produce larger plants if stands become thin or when planted in wide rows, and they seem to be more sensitive to moisture stress than upland cultivars.[9]

In native prairies, switchgrass is historically found in association with several other important native

prairie clover, and prairie coneflower). These widely adapted tallgrass species once occupied millions of hectares.[10]

Switchgrass’ suitability for cultivation in the

Instituto Nacional de Tecnología Agropecuaria (INTA).[11]

Establishment and management

Switchgrass can be grown on land considered unsuitable for

no-till and conventional tillage. When seeded as part of a diverse mixture, planting guidelines for warm-season grass mixtures for conservation plantings should be followed. Regional guidelines for growing and managing switchgrass for bioenergy or conservation plantings are available. Several key factors can increase the likelihood of success for establishing switchgrass. These include:[12]

2,4-D, should be avoided as they are known to reduce development of switchgrass when applied early in the establishing year.[13] Plantings that appear to have failed due to weed infestations are often wrongly assessed, as the failure is often more apparent than real. Switchgrass stands that are initially weedy commonly become well established with appropriate management in subsequent years.[12]
Once established, switchgrass can take up to three years to reach its full production potential.[14] Depending on the region, it can typically produce 1/4 to 1/3 of its yield potential in its first year and 2/3 of its potential in the year after seeding.[15]

After establishment, switchgrass management will depend on the goal of the seeding. Historically, most switchgrass seedings have been managed for the

field equipment used for hay production, and it is well-suited to baling or bulk field harvesting. If its biology is properly taken into consideration, switchgrass can offer great potential as an energy crop.[12][16]

Uses

Switchgrass can be used as a

ground cover for soil conservation, and to control erosion, for forages and grazing, as game cover, and as feedstock for biodegradable plastics. It can be used by cattle farmers for hay and pasture and as a substitute for wheat straw in many applications, including livestock bedding, straw bale housing, and as a substrate for growing mushrooms.

Panicum virgatum 'Heavy Metal', an ornamental switchgrass, in early summer

Additionally, switchgrass is grown as a drought-resistant ornamental grass

in average to wet soils and in full sun to part shade.

Moth host plant

It is the preferred larval host plant of

Delaware skipper and the Hobomok skipper.[18]

Bioenergy

Switchgrass has been researched as a renewable

fossil energy compared to grain corn's 2.9 GJ/ODT.[21] Given that switchgrass contains approximately 18.8 GJ/ODT of biomass, the energy output-to-input ratio for the crop can be up to 20:1.[22]
This highly favorable ratio is attributable to its relatively high energy output per hectare and low energy inputs for production.

Considerable effort is being expended in developing switchgrass as a

US$100 million has been invested into researching switchgrass as a potential biofuel source.[26] Switchgrass has the potential to produce up to 380 liters of ethanol per tonne harvested.[27] However, current technology for herbaceous biomass conversion to ethanol is about 340 liters per tonne.[28] In contrast, corn ethanol yields about 400 liters per tonne.[29]

The main advantage of using switchgrass over corn as an ethanol feedstock is its cost of production is generally about 1/2 that of grain corn, and more biomass energy per hectare can be captured in the field.

energy balance is also considered to be substantially better than that of corn ethanol. During the bioconversion process, the lignin fraction of switchgrass can be burned to provide sufficient steam and electricity to operate the biorefinery. Studies have found that for every unit of energy input needed to create a biofuel from switchgrass, four units of energy are yielded.[30] In contrast, corn ethanol yields about 1.28 units of energy per unit of energy input.[31] A recent study from the Great Plains [32] indicated that for ethanol production from switchgrass, this figure is 6.4, or alternatively, that 540% more energy was contained in the ethanol produced than was used in growing the switchgrass and converting it to liquid fuel. However, there remain commercialization barriers to the development of cellulosic ethanol technology. Projections in the early 1990s for commercialization of cellulosic ethanol by the year 2000[33] have not been met. The commercialization of cellulosic ethanol is thus proving to be a significant challenge, despite noteworthy research efforts.

Thermal energy applications for switchgrass appear to be closer to near-term scale-up than cellulosic ethanol for industrial or small-scale applications. For example, switchgrass can be

wood pellet shortages throughout Eastern North America. Generally speaking, the direct firing of switchgrass for thermal applications can provide the highest net energy gain and energy output-to-input ratio of all switchgrass bioconversion processes.[37] Research has found switchgrass, when pelletized and used as a solid biofuel, is a good candidate for displacing fossil fuels. Switchgrass pellets were identified to have a 14.6:1 energy output-to-input ratio, which is substantially better than that for liquid biofuel options from farmland.[21] As a greenhouse gas mitigation strategy, switchgrass pellets were found to be an effective means to use farmland to mitigate greenhouse gases on the order of 7.6-13 tonnes of CO2 per hectare. In contrast, switchgrass cellulosic ethanol and corn ethanol were found to mitigate 5.2 and 1.5 tonnes of CO2 per hectare, respectively.[16]

Historically, the major constraint to the development of grasses for thermal energy applications has been the difficulty associated with burning grasses in conventional

harvesting that allow for leaching to occur, which leads to fewer aerosol-forming compounds (such as K and Cl) and N in the grass. This reduces clinker formation and corrosion, and enables switchgrass to be a clean combustion fuel source for use in smaller combustion appliances. Fall harvested grasses likely have more application for larger commercial and industrial boilers.[38][39][40] Switchgrass is also being used to heat small industrial and farm buildings in Germany and China through a process used to make a low quality natural gas substitute.[41]

Bai et al. (2010) conducted a study to analyze the environmental sustainability of using switchgrass plant material as a feedstock for

E10, E85, and ethanol with gasoline. They took into account air and water emissions associated with growing, managing, processing and storing the switchgrass crop. They also factored in the transportation of the stored switchgrass to the ethanol plant where they assumed the distance was 20 km. The reductions in global warming potential
by using E10 and E85 were 5 and 65%, respectively. Their models also suggested that the “human toxicity potential” and “eco-toxicity potential” were substantially greater for the high ethanol fuels (i.e., E85 and ethanol) than for gasoline and E10.

In 2014, a genetically altered form of the bacterium Caldicellulosiruptor bescii was created which can cheaply and efficiently turn switchgrass into ethanol.[43][44]

Biodegradable plastics production

In a novel application, US scientists have genetically modified switchgrass to enable it to produce polyhydroxybutyrate, which accumulates in beadlike granules within the plant's cells.[45] In preliminary tests, the dry weight of a plants leaves were shown to comprise up to 3.7% of the polymer.[46] Such low accumulation rates do not, as of 2009, allow for commercial use of switchgrass as a biosource.

Soil conservation

Further information:
Restoration ecology, and Revegetation

Switchgrass is useful for

amendment, particularly in the United States and Canada, where switchgrass is endemic. Switchgrass has a deep fibrous root system – nearly as deep as the plant is tall. Since it, along with other native grasses and forbs, once covered the plains of the United States that are now the Corn Belt, the effects of the past switchgrass habitat have been beneficial, lending to the fertile farmland that exists today. The deep fibrous root systems of switchgrass left a deep rich layer of organic matter in the soils of the Midwest, making those mollisol
soils some of the most productive in the world. By returning switchgrass and other perennial prairie grasses as an agricultural crop, many marginal soils may benefit from increased levels of organic material, permeability, and fertility, due to the grass's deep root system.

Soil erosion, both from wind and water, is of great concern in regions where switchgrass grows. Due to its height, switchgrass can form an effective wind erosion barrier.[47] Its root system, also, is excellent for holding soil in place, which helps prevent erosion from flooding and runoff. Some

Conservation districts
in many parts of the United States use it to control erosion in grass waterways because of its ability to anchor soils while providing habitat for wildlife.

Forages and grazing

Switchgrass is an excellent

saponins, which cause photosensitivity
and liver damage in these animals. Researchers are continuing to learn more about the specific conditions under which switchgrass causes harm to these species, but until more is discovered, it is recommended switchgrass not be fed to them. For cattle, however, it can be fed as hay, or grazed.

Grazing switchgrass calls for watchful management practices to ensure survival of the stand. It is recommended that grazing begin when the plants are about 50 cm tall, and that grazing be discontinued when the plants have been eaten down to about 25 cm, and to rest the pasture 30 – 45 days between grazing periods.[52] Switchgrass becomes stemmy and unpalatable as it matures, but during the target grazing period, it is a favorable forage with a relative feed value (RFV) of 90-104.[53] The grass's upright growth pattern places its growing point off the soil surface onto its stem, so leaving 25 cm of stubble is important for regrowth. When harvesting switchgrass for hay, the first cutting occurs at the late boot stage – around mid-June. This should allow for a second cutting in mid-August, leaving enough regrowth to survive the winter.[54]

Game cover

Switchgrass is well known among wildlife conservationists as good forage and habitat for upland

game bird species, such as pheasant, quail, grouse, and wild turkey, and song birds, with its plentiful small seeds and tall cover. A study published in 2015 has shown that switchgrass, when grown in a traditional monoculture, has an adverse impact on some wildlife.[55] Depending on how thickly switchgrass is planted, and what it is partnered with, it also offers excellent forage and cover for other wildlife across the country. For those producers who have switchgrass stands on their farm, it is considered an environmental and aesthetic benefit due to the abundance of wildlife attracted by the switchgrass stands. Some members of Prairie Lands Bio-Products, Inc. in Iowa have even turned this benefit into a profitable business by leasing their switchgrass land for hunting during the proper seasons.[56] The benefits to wildlife can be extended even in large-scale agriculture through the process of strip harvesting, as recommended by The Wildlife Society, which suggests that rather than harvesting an entire field at once, strip harvesting could be practiced so that the entire habitat is not removed, thereby protecting the wildlife inhabiting the switchgrass.[57]

Ornamental cultivars

Panicum virgatum cultivars are used as ornamental plants in gardens and landscaping. The following have gained the Royal Horticultural Society's Award of Garden Merit:-

See also

References

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  2. ^ Silzer, Tanya (January 2000). "Panicum virgatum L., Switchgrass, prairie switchgrass, tall panic grass". Rangeland Ecosystems & Plants Fact Sheets. University of Saskatchewan Department of Plant Sciences. Retrieved 2007-12-08.
  3. ^ a b Secter, Bob. "Plentiful switch grass emerges as breakthrough biofuel". The San Diego Union-Tribune. Retrieved 2008-05-24.
  4. ^ a b Uchytil, Ronald J. (1993). "Panicum virgatum". Fire Effects Information System (FEIS). US Department of Agriculture (USDA), Forest Service (USFS), Rocky Mountain Research Station, Fire Sciences Laboratory. Retrieved 2018-07-13.
  5. ^ Ernst Seed Catalog Web Page (2007). "Switchgrass and Warm Season Grass Planting Guide". Ernst Conservation Seeds. Archived from the original on 2007-08-03. Retrieved 2007-12-08.
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  7. ^ USDA, NRCS (n.d.). "Panicum virgatum". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team. Retrieved 2008-05-21.
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  9. ^ Establishing and Managing Switchgrass as an Energy Crop, Forage and Grazinglands, 2008.
  10. ^ Switchgrass as a Bioenergy Crop, ATTRA - National Sustainable Agricultural Information Service, 2006.
  11. ^ "Aprovechamiento de recursos vegetales y animales para la produccion de biocombustibles" (PDF) (in Spanish). INTA. 26 June 2008. Archived from the original (PDF) on 26 September 2010.
  12. ^ a b c http://reap-canada.com/online_library/feedstock_biomass/5-Establishing%20and%20Managing%20Switchgrass%20as%20an%20Energy%20Crop%20_Parrish%20et%20al.,%202008.pdf David J. Parrish, John H. Fike, David I. Bransby, Roger Samson. Establishing and Managing Switchgrass as an Energy Crop. Forage and Grazinglands. 2008
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  17. ^ "Archived copy" (PDF). Archived from the original (PDF) on 2017-06-08. Retrieved 2018-01-05.{{cite web}}: CS1 maint: archived copy as title (link)
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  23. ^ Adrienne Mand Lewin (2006-02-01). "Switchgrass: The Super Plant Savior?". ABC News.
  24. National Public Radio
    . 2006-02-01.
  25. ^ Dana Bash; Suzanne Malveaux; et al. (2006-02-01). "Bush has plan to end oil 'addiction'". CNN.
  26. ^ "Since that mention in the 2006, investment in switch grass has exploded, thanks in large part, experts say, to the President's speech. Venture capitalists have poured over $100 million into private companies that are exploring the technology necessary to convert switchgrass into fuel, and large publicly owned companies are also directing their research dollars into biofuels."Jessica Yellin; Katie Hinman; Nitya Venkataraman (2007-01-23). "What Happened to Bush Call for Switchgrass?". ABC News.
  27. ^ "Switchgrass: Native American Powerhouse?". Renewable Energy Resources. Retrieved 2007-01-05.
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  31. ^ Wang, M., Wu, M., & Huo, H. Life-cycle energy and greenhouse gas emission impacts of different corn ethanol plant types. Environmental Research Letters. Volume 2. 2007. 1-13.
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  34. ^ "Home". iowaswitchgrass.com.
  35. ^ Show Me Energy Cooperative
  36. ^ Bailey Stamler, S., R. Samson and C. Ho Lem. Biomass resources options: Creating a BIOHEAT supply for the Canadian greenhouse industry. Final report to Natural Resources Canada, Ottawa. 2006. 38 pages
  37. ^ "Archived copy" (PDF). Archived from the original (PDF) on 2010-05-08. Retrieved 2009-03-10.{{cite web}}: CS1 maint: archived copy as title (link) Samson, R., and S. Bailey Stamler. Going Green for Less: Cost-Effective Alternative Energy Sources. C.D. Howe Institute Commentary 282. Economic Growth and Innovation. 2009. 25 pages
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  39. ^ "Samson et al., 2008": In regions where the potassium and chlorine contents of switchgrass cannot be successfully leached out for thermal applications, it may be that biogas applications for switchgrass will prove more promising. Switchgrass has demonstrated some promise in biogas research as an alternative feedstock to whole plant corn silage for biogas digesters.
  40. ^ "Frigon et al. 2008 http://www.gtmconference.ca/site/downloads/2008presentations/5B3%20-Frigon.pdf Archived 2016-03-03 at the Wayback Machine J.C. Frigon, P. Mehta, S.R. Guiot. The bioenergy potential from the anaerobic digestion of switchgrass and other energy crops. National Research Council Canada. Growing the Margins Conference: Energy, Bioproducts and Byproducts from farms and food sectors. April 2–5, 2008, London, Ontario
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  43. ^ "Bacteria take plants to biofuel in one step". Science News. 3 June 2014. Retrieved 2014-06-04.
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  47. ^ a b "Plant Fact Sheet, Panicum virgatum (switchgrass)" (PDF). United States Department of Agriculture, Natural Resources Conservation Service, Plant Materials Program. 2006-05-06. Retrieved 2008-05-21.
  48. ^ "KDOT Bid Tabs". Kansas Department of Transportation. Retrieved 2008-05-20.
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  52. ^ Ball, D.M.; Hoveland, C.S.; Lacefield, G.D. (2006). "Table 28. Guidelines for rotational stocking of selected forage crops". Forage Crop Pocket Guide. International Plant Nutrition Institute.
  53. ^ Ball, D.M.; Hoveland, C.S.; Lacefield, G.D. (2006). "Table 33b. Total Digestible Nutrients (TDN) and Relative Feed Value (RFV) Ranges for Various Forage Crops". Forage Crop Pocket Guide. International Plant Nutrition Institute.
  54. ^ Wolf, D.D.; Fiske, D.A. (1995). "Planting and managing switchgrass for forage, wildlife, and conservation" (PDF). Virginia Cooperative Extension Publication: 418–013. Archived from the original (PDF) on 2008-05-17. Retrieved 2008-05-24.
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  58. ^ "Panicum virgatum 'Dallas Blues'". RHS. Retrieved 18 January 2021.
  59. ^ "Panicum virgatum 'Heavy Metal'". RHS. Retrieved 18 January 2021.
  60. ^ "Panicum virgatum 'Hänse Harms'". RHS. Retrieved 18 January 2021.
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  62. ^ "Panicum virgatum 'Shenandoah'". RHS. Retrieved 18 January 2021.

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