Panicum virgatum

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Switchgrass
Scientific classification
Kingdom: Plantae Division: Magnoliophyta Class: Liliopsida Order: Poales Family: Poaceae Genus: Panicum Species: P. virgatum
Binomial name
Panicum virgatum L.

Panicum virgatum, commonly known as switchgrass, is a warm season grass and is one of the dominant species of the central North American tallgrass prairie. It can be found in remnant prairies, along roadsides, pastures and as an ornamental plant in gardens. Other common names for it include tall panic grass, Wobsqua grass, lowland switchgrass, blackbent, tall prairiegrass, wild redtop and thatchgrass. In his 2006 State of the Union Address, President George W. Bush touted switchgrass as an efficient and environmentally friendly biofuel that could reduce the USA's dependence on petroleum.

Contents 1 Properties 2 Uses 3 Background 3.1 Distribution 3.2 Soil conservation 3.3 Game cover 3.4 Preservation of native plant species 3.5 Biofuel 3.6 Forages 4 Establishment 5 See also 6 References 7 External links

[edit] Properties

Switchgrass is a hardy, perennial rhizomatous grass which begins growth in late spring. It can grow up to 1.8-2.2 m high but is typically shorter than Big Bluestem grass or Indiangrass. The leaves are 30-90 cm long, with a prominent midrib. Switchgrass uses C4 carbon fixation, giving it an advantage in conditions of drought and high temperature.^[1] Its flowers have a well-developed panicle, often up to 60 cm long and bear a good crop of fruits. The fruits are 3-6 mm long and up to 1.5 mm wide, and are developed from a single-flowered spikelet. Both glumes are present and well developed. When ripe, the seeds sometimes take on a pink or dull-purple tinge, and turn golden brown with the foliage of the plant in the fall. Switchgrass is a self-seeding crop, which means farmers do not have to plant and re-seed after annual harvesting. Once established, a switchgrass stand can survive for ten years or longer.^[2] Also, unlike corn, switchgrass can grow on marginal lands and requires little or no fertilizer to thrive.^[2]

[edit] Uses

Switchgrass is grazed by certain animals, used as ground cover to control erosion, farmed as forage for livestock.

Switchgrass is rich in cellulose, making it attractive as a source for cellulosic ethanol.^[3] It is at the core of an alternative fuel strategy announced by Tennessee Governor Phil Bredesen in January 2007.^[4]

As a drought resistant ornamental grass, it is easily grown in average to wet soils and in full sun to part shade. Establishment is recommended in the spring, at the same time as corn is planted.

[edit] Background

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Much of North America, especially the prairies of the Midwest, was once home to vast swaths of native grasses including Switchgrass (Panicum virgatum), Indiangrass (Sorghastrum nutans), Eastern Gamagrass (Tripsacum dactyloides), Big Bluestem (Andropogon gerardii), Little Bluestem (Schizachyrium scoparium) and others. As settlers began spreading out across the continent, the native grasses were replaced by crops such as corn and wheat. Introduced grasses such as fescue, bluegrass, and orchardgrass ^[5] replaced the native grasses.

Today, as biofuels are becoming a mainstay in the headlines, the public is hearing about Switchgrass as an excellent prospect for providing ethanol for our cars. There are also other benefits and opportunities for switchgrass in our economy.

[edit] Distribution

Switchgrass is very versatile and adaptable. 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 Saskatchewan to Nova Scotia and south over most of the United States east of the Rocky Mountains.^[6] As a warm season perennial grass, most of its growth occurs from late spring through early fall and becomes dormant and unproductive during colder months. Thus, the productive season in the northern regions can be as short as three months, but up to eight months in the Gulf Coast area.^[7]

[edit] Soil conservation

Further information: Mine reclamation, Restoration ecology, and Revegetation

Switchgrass is useful for soil conservation and 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, one could say that they still help feed the world today. Their deep fibrous roots left a very deep rich layer of organic matter in the soils; making those mollisol soils some of the most productive in the world. By returning switchgrass and other perennial prairie grasses to the agricultural scene, many marginal soils will benefit from their deep root systems through increased organic matter levels, permeability, and fertility.

Soil erosion, both from wind and water, is of great concern in regions where switchgrass can grow. Due to its height, switchgrass can form the low part of a wind erosion barrier.^[8] Its root system is excellent for holding soil in place. Some highway departments (for example, KDOT) have used it in their seed mixes when re-establishing growth along roadways.^[9] It can also be used on strip mine sites, dikes^[8], and pond dams. Conservation districts in many parts of the United States use it to control erosion in grass waterways because of its excellent ability to anchor soils while also doubling as native habitat for wildlife.

[edit] Game cover

Switchgrass is well-known among wildlife conservationists as a favorite among the upland game bird species such as pheasant, quail, grouse and song birds. Its small seeds are well-liked among them. Wild turkeys are also commonly found in Switchgrass stands. Depending on how thickly switchgrass is planted, and what it is partnered with, it can offer excellent forage and cover for a wide variety of other wildlife across the country. For those producers who have switchgrass stands on their farm, they consider this benefit an aesthetic one as much as an environmental one because they enjoy watching the wildlife. Some members of Prairie Lands Bio-Products, Inc. in Iowa have even turned this benefit into a profitable one by leasing their switchgrass land for hunting during the proper seasons.^[10] In an agricultural setting, like growing many acres of switchgrass for biofuel, the advantages to wildlife can still stand. Although the Wildlife Society suggests that rather than harvest an entire field at once, strip harvesting could be practiced so the entire habitat is not removed at one time for the wildlife that have made the switchgrass their home.^[11]

[edit] Preservation of native plant species

There is another type of conservation that doesn't draw as much attention as soil and wildlife conservation normally does: the conservation of our native plant species, such as switchgrass. By bringing switchgrass to the front of the news, Americans are revisiting a part of their nation's past that many have perhaps never thought about: when North American was covered in "that vast seas of grasses, so thick and high that pioneers said it could swallow a rider on horseback."^[2] Maybe this will stir interest by a broader spectrum of the population in switchgrass and other native species that were once a part of our landscape which have gone to the wayside. Several groups help inform the public about native plant species, such as a scholarly group at the University of Idaho which publishes the Native Plants Journal^[12] to educate the public about native plant species, as well as groups like Grow Native!,^[13] international organizations such as the National Audubon Society, and state organizations like the Virginia Native Plant Society.^[14] These groups offer information and anecdotes about native species' habitat, history, pests, growth patterns, positive and negative attributes.

[edit] Biofuel

Switchgrass is often considered a good candidate for biofuel — especially ethanol fuel — production due to its hardiness against poor soil and climate conditions, rapid growth and low fertilization and herbicide requirements. Switchgrass is also perennial, unlike corn, and has a huge biomass output, the raw plant material used to make biofuel, of 6-10 tons per acre.^[15][2] President George W. Bush mentioned this usage in his 2006 State of the Union address ^{[16] [17][18]}; since then, over $100 million has been invested into researching the potential fuel source^[19].

Switchgrass has the potential to produce the biomass required for production of up to 100 gallons (380 liters) of ethanol per metric ton.^[20] This gives switchgrass the potential to produce 1000 gallons of ethanol per acre, compared to 665 gallons for sugarcane and 400 gallons for corn.^[21]

However, there is debate on the viability of switchgrass, and all other biofuels, as an efficient energy source. University of California, Berkeley professor Tad Patzek argues that switchgrass has a negative ethanol fuel energy balance, requiring 45 percent more fossil energy than the fuel produced.^[22] On the other side, David Bransby, professor of energy crops at Auburn University, has found that for every unit of energy input, switchgrass yields four units out.^[23] In a 2007 lecture Professor Richard Muller, also of the University of California, Berkeley, noted that it is the conversion of switchgrass biomass into ethanol which introduces significant inefficiencies. He also noted that The Helios Project at Lawrence Berkeley Laboratory is actively trying to engineer metabolic pathways in bacteria to more efficiently convert cellulose to ethanol. Bransby's work was the source for President Bush's comments in the 2006 State of the Union address.

Switchgrass is 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.^[2] It can also be pressed into fuel pellets which are burned in pellet stoves used to heat homes, which typically burn corn or wood pellets.^[24]

In the spring of 2008, 1,000 acres (4.0 km²) of switchgrass will be planted near Guymon, Oklahoma, in the Oklahoma Panhandle to study the feasibility of utilizing the crop for biofuel. It will be the largest stand ever planted for such purposes. The project is being spearheaded by the Oklahoma Bioenergy Center, a state project backed by Governor Brad Henry.^[25]

[edit] Forages

Switchgrass is an excellent forage for cattle; however, it has shown toxicity in horses, sheep and goats^[26][27][28] through chemical compounds known as saponins, which cause photosensitivity and liver damage in these animals. Researchers are continuing to learn more about the specific conditions under which the switchgrass must be in order to cause harm to these species, but until more is discovered, it is recommended that 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 there is 18 – 22 inches of growth, to stop grazing when there are 8 – 12 inches of stubble left, and to rest the pasture 30 – 45 days between grazing periods^[29]. Switchgrass becomes very stemmy and unpalatable as it matures, but during the target grazing period, it is a highly favorable forage with a relative feed value (RFV) of 90-104^[30]. The grass' upright growth pattern places its growing point off the soil surface onto its stem, so leaving 8 – 12 inches 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.^[31]

[edit] Establishment

Once established, it takes three years for a stand of switchgrass to reach its full potential^[24]. According to David Bransby at Auburn University, it will produce a quarter to a third of its full potential in its first year and two-thirds in its second year^[32]. It is sometimes suggested that the stand not be harvested during the establishment year^[24]. Afterwards, each region has its own recommendations for fertilizer rates. The timing of harvesting depends upon how the switchgrass is to be used, and weed control can be addressed with limited herbicides, controlled burns, and mechanical methods.

[edit] See also

• Algae fuel
• Brachypodium distachyon
• Energy crop
• Proceedings of the National Academy of Sciences

[edit] References

[edit] External links

• Switchgrass Fuel Yields Bountiful Energy
• "Switchgrass: A Living Solar Battery." Roger Samson (Online reprint)
• http://bioenergy.ornl.gov/papers/misc/switchgrass-profile.html
• Economics of switchgrass production
• USDA Studies Switchgrass for Ethanol and Energy Production
• Switchgrass as an Alternative Energy crop - European Union study on Switchgrass feasibility.
• Switchgrass images - Archive of Central Texas Plants
• Switchgrass images - Has closeup photos of spikelets
• Switch Grass Information Repository - General information repository on switch grass usage and feasible application as an alternative energy
• "Grass Makes Better Ethanol than Corn Does" - Scientific American article on the potential use of switchgrass for biofuels
• Study Shows Great Potential of Switchgrass as Biofuel Feedstock

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