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

Switchgrass (Panicum virgatum) 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 oil.

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 harvesting.[1] Also, unlike corn, switchgrass can grow on marginal lands and require little or no fertilizer to thrive.

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.^[2] It is at the core of an alternative fuel strategy announced by Tennessee Governor Phil Bredesen in January 2007.^[3]

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.

For corporal punishment, a "switch", a lengthy yet strong stem of switch grass, may be cut from the trunk of the plant, pruned and used as a whip.

Background

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 ^[4] replaced the native grasses. Today, as [biofuel]s 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.

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 55ºN from Saskatchewan to Nova Scotia and south over most of the United States east of the Rocky Mountains (Sizler, 2007) 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 (Ball et al., 2002).

One of the benefits of switchgrass is through soil amendment and conservation. 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, you 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.

As soil erosion, both from wind and water, is of great concern in all regions, the adaptability of Switchgrass is very appealing. Due to its height, it can be used as a low part of a wind erosion barrier (USDA NRCS, 2001). Its root system is excellent for holding soil in place. Some highway departments have used it in their seed mixes when re-establishing growth along roadways (Kansas Department of Transportation). It can also be used on strip mine sites, dikes(4), and pond dams. Conservation districts are already using it in many parts of the country to control erosion in grass waterways because of its excellent ability to anchor soils while also doubling as native habitat for wildlife.

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 (6). 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 (7).

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, we are revisiting a part of our 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."(19) 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. There are groups dedicated to helping inform the public about native plant species, such as this scholarly group at the University of Idaho who has a published the Native Plants Journal and its online twin http://nativeplants.for.uidaho.edu/ dedicated to educating the public about native plant species (8), as well as groups with web sites like www.grownative.org, international organizations such as the National Audubon Society, and state organizations like the Virginia Native Plant Society. These groups can offer information about native species' habitat, pests, growth patterns, positive attributes and negative ones. They can also offer some interesting tidbits of history and anecdotes about some plants.

Biofuel

Panicum virgatum 'Heavy Metal' switchgrass in early summer

Cellulosic ethanol (also called lignocellulosic ethanol, or ceetoh) is a type of biofuel produced from lignocellulose, a structural material that comprises much of the mass of plants. Lignocellulose is composed mainly of cellulose, hemicellulose and lignin. Corn stover, switchgrass, miscanthus and woodchip are some of the more popular cellulosic materials for ethanol production. Cellulosic ethanol is chemically identical to ethanol from other sources, such as corn starch or sugar, but has the advantage that the lignocellulose raw material is highly abundant and diverse. However, it differs in that it requires a greater amount of processing to make the sugar monomers available to the microorganisms that are typically used to produce ethanol by fermentation.

Switchgrass is the major biomass material being studied today, due to its high levels of cellulose.

In March 2007, the US government awarded $385 million in grants aimed at jumpstarting ethanol production from nontraditional sources like wood chips, switchgrass and citrus peels. Half of the six projects chosen will use thermo-chemical methods and half will use cellulosic ethanol methods.^[15]

Some think that even land marginal for agriculture could be planted with cellulose-producing crops like switchgrass, resulting in enough production to substitute for all the current oil imports into the United States.^[16]

Today, there is only a small amount of switchgrass dedicated for ethanol production. In order for it to be grown on a large-scale production it must compete with existing uses of agricultural land, mainly for the production of crop commodities. Of the United States 2 billion acres of land, 33% are forestland, 26% pastureland and grassland, and 20% crop land. A study done by the U.S. Departments of Energy and Agriculture in 2005, determined whether there were enough available land resources to sustain production of over 1 billion dry tons of biomass annually to replace 30% or more of the nation’s current use of liquid transportation fuels. The study found that there could be 1.3 billion dry tons of biomass available for ethanol use, by making little changes in agricultural and forestry practices and meeting the demands for forestry products, food, and fiber.^[17]

Cellulose is not used for food and can be grown in all parts of the world. The entire plant can be used when producing cellulosic ethanol. Switchgrass yields twice as much ethanol per acre than corn.^[18] Therefore, less land is needed for production and thus less habitat fragmentation. Biomass materials require fewer inputs, such as fertilizer, herbicides, and other chemicals that can pose risks to wildlife. Their extensive roots improve soil quality, reduce erosion, and increase nutrient capture. Herbaceous energy crops reduce soil erosion by greater than 90%, when compared to conventional commodity crop production. This can translate into improved water quality for rural communities. Additionally, herbaceous energy crops add organic material to depleted soils and can increase soil carbon, which can have a direct effect on climate change.^[19] As compared to commodity crop production, biomass reduces surface runoff and nitrogen transport. Switchgrass provides an environment for diverse wildlife habitation, mainly insects and ground birds. Conservation Resource Program (CRP) land is composed of perennial grasses, which are used for cellulosic ethanol, and may be available for use.

Switchgrass is a native prairie grass that is known for its hardiness and rapid growth. This perennial grows during the warm season of the year and grows to 2-6 feet tall. Switchgrass can be grown in most parts of the United States, including swamplands, plains, streams, and along the shores. It is resistant to many diseases and pests and can produce high yields with low applications of fertilizer and other chemicals. It is also tolerant to poor soils, flooding, and drought and improves soil quality and prevents erosion.^[19]

Switchgrass is an approved cover crop for land protected under the federal Conservation Reserve Program (CRP). CRP is a government program that pays producers a fee for not growing crops on land on which crops recently grew. This program reduces soil erosion, enhances water quality, and increases wildlife habitat. CRP land serves as a habitat for upland game, such as pheasants and ducks, and a number of insects. Switchgrass for biofuel production has been considered for use on Conservation Reserve Program (CRP) land, which could increase ecological sustainability and lower the cost of the CRP program. However, CRP rules would have to be modified to allow this economic use of the CRP land.^[19]

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.^[5][6] President George W. Bush mentioned this usage in his 2006 State of the Union address ^{[7] [8][9]}; since then, over $100 million has been invested into researching the potential fuel source^[10].

Switchgrass has the potential to produce the biomass required for production of up to 100 gallons (380 liters) of ethanol per metric ton.^[11] This gives switchgrass the potential to produce 1000 gallons of ethanol per acre, compared to 665 gallons for sugarcane and 400 gallons for corn.^[12]

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.^[13] 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.^[14] 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. It is Bransby's work that 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 (19). It can also be pressed into fuel pellets which are burned in special furnaces used to heat homes, which typically use corn or wood pellets (9).

Forages

Switchgrass is an excellent forage for cattle; however, it has shown toxicity in horses, sheep and goats (10, 11, 12) 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 (13). 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 (14). 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. (15)

Establishment & Management

Switchgrass stands can last for many years. The rhizome root system grows deeply into the soil and the plant efficiently uses the C4 cycle to fix carbon through photosynthesis for energy production. But establishment takes the proper steps and patience.

The first step is choosing your planting method, which will then determine how you prepare your seedbed. Various states' Extension Services recommend different planting methods for switchgrass for their regions, including tillage, no-till, broadcast and sod-seedling (15, 16, 17, 18). No matter which is used, initial weed control is essential since switchgrass is slow to establish, and the use of broadleaf herbicides over the switchgrass seedlings could cause the crop great damage. The seeding rate is five to six pounds of pure live seed (PLS) per acre in the spring (April – May) at ¼ - ½ inch planting depth (3). There are approximately 280,000 switchgrass seed per pound (3). Fortunately, the seed is large and smooth enough that it can be planted with most drills (16). Therefore, farmers choosing to move some of their acres into this crop for either biofuel or other reasons may not have to purchase a new piece of equipment. Germination occurs in approximately 5 – 7 days (15). No fertilizer is required in the establishment year, nor is it recommended: switchgrass is very efficient at utilizing the available nutrients in the soil and adding fertilizer would only increase the weed competition (9).

Once established, it takes three years for a stand of switchgrass to reach its full potential (9). 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 (20). It is sometimes suggested that the stand not be harvested during the establishment year (9). 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.

After the stand is successfully established, which takes good management practices and patience, a healthy stand of switchgrass is there to benefit man, animal, and Earth.

See also

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

References

  Wolf, DD, Fiske, DA. Virginia Cooperative Extension Publication # 418-013,