Warm Season Prairie Grasses

Prairie Grass Primer

The Great Plains of North America is one of the largest expanses of grassland in the world. It extends westward from the deciduous forest of the Appalachian Mountains to the foothills of the Rocky Mountains and southward from Canada to Mexico. 

The east-to-west gradient of increasing altitude, decreasing precipitation, and increasing temperature and the north-to-south gradient of temperature and humidity have created zones of tall-, medium-, and short-grass prairies. This vast prairie region is comprised chiefly of warm-season grasses which tolerate climatic extremes. 

Tall Grass Prairie
Historically, the tall-grass prairie consisted of big and little bluestem, switchgrass, and indiangrass. These species thrive in zones of 30-40-inch annual precipitation and reach 6-8 feet in height. Within this zone, cordgrass (Stipa spp.) and reed grass (Phragmites spp.) are dominant species in the wetlands. Thousands of years of tall-grass dominance (owing to managed and natural fires preventing forest development) created a rich, fertile soil which now characterizes the corn belt of the USA. forages.orst.edu/projects/regrowth/main.cfm?PageID=31

The Great Plains of the central U.S. were originally dominated by prairie ecosystems. A map of the Great Plains can be seen at www.gpisd.net/about/great_plains_map.htm.  The tall-grass region on the eastern side of the Great Plains offers the greatest potential for producing biomass energy at potentially competitive cost. A useful precipitation map that helps define the tall-grass region can be viewed at forages.orst.edu/projects/regrowth/images/us_precip.gif .

Current Land Use in the Region

Only small remnants of the original tall-grass prairie remain, most of it having been broken by the plow and converted to intensive agricultural use. Current land-use information is available from several sources. The Land Use Land Cover (LULAC) data set is available from USGS . A statewide LULAC map of Kansas showing 10 different land uses is available at gisdasc.kgs.ukans.edu/dasc/kanviewframe.html . A newer data set from the GAP project shows many more land-cover classes. G AP is the acronym used to refer to the Gap Analysis Program of USGS. A map that will help you find GAP data for individual states can be found at www.gap.uidaho.edu/Projects/States/default.htm . GAP data for Kansas showing 43 land-cover classes can be found at mapster.kgs.ukans.edu/dasc/catalog/coredata.html.

C4 vs C3 Grasses

Grasses use one of two somewhat different photosynthetic processes. Melvin Calvin detailed the reductive pentose phosphate (RPP) cycle in the 1950s, typically referred to as the C3 cycle.  Orchardgrass, fescues, and perennial ryegrass are examples of C3, or cool season, grasses.  Other grasses that have evolved more recently use a generally more efficient process referred to as C4.  Examples of C4 grasses include big bluestem, indiangrass, bermudagrass, switchgrass, and annuals like corn and sudan grass. For a detailed discussion of photosynthesis, refer to Vaclav Smil's General Energetics: Energy in the Biosphere and Civilization.   Michael Anderson's Grass Leaf Morphology presentation at www.teaching.ag.iastate.edu/hort551/grass_leaf/ provides a more abbreviated explanation. C4 plants have the following characteristic that make them potentially attractive biomass energy plants (although some research suggests that increasing atmospheric CO2 associated with global warming may change some of these):

Switchgrass

Switchgrass (panicum virgatum) has become the prima donna of perennial, biomass energy prairie grasses. High yields, lower ash content than some other grasses, and the need for consistent chemical composition in applications like utility co-firing have pushed several varieties of switchgrass to first choice in many people's opinions. In other applications such as pelleting, it may make sense to consider a more diverse feedstock, such as a traditional mixture of switchgrass, big bluestem, indiangrass, and limited forbes.  Such a mixture may complicate pellet-fuel quality control, but it could dramatically expand the amount of harvestable prairie land.  A monocrop of switchgrass may significantly reduce erosion, improve water quality, sequester carbon, and achieve the highest biomass yield, but it is still a monocrop of limited ecosystem diversity. Such a monocrop would have to compete with conventional commodity grain crops or acquire a waiver of planting criteria and harvest restrictions from the Conservation Reserve Program (CRP). 

Information on switchgrass varieties can be found at Oregon State University's Forage Information System Web site at forages.orst.edu/main.cfm?PageID=180&specID=26 and the USDA's Plants Profile site at plants.usda.gov/cgi_bin/plant_profile.cgi?symbol=PAVI2.

Sharp Seed Company Switchgrass Fact Sheet

www.sharpseed.com/seedpdf/switchgrass.html

 

Sharp Seed Company Big Bluestem Fact Sheet

www.sharpseed.com/seedpdf/bigbluestem.html

Yield Potential

DOE's Biofuels Development Program at Oak Ridge National Laboratory and others have funded extensive switchgrass field trials in the U.S. Results of some of these trials are summarized in the table below.

Note: Except for Fritz and Teel data for Kansas and Iowa, data in Table 2.3.2 are from the ORNL database

provided by Anne Ehrenshaft. Failed stands are not included. Only single annual harvest data are shown above.

An Assessment of the Feasibility of Electric Power Derived from Biomass and Waste Feedstocks
King, J., M. Hanninfan, and R. Nelson,
for Kansas Electric Utilities Research Program,
Kansas Corporation Commission Energy Programs Division,
Western Regional Biomass Energy Program, 1998.

Developing Switchgrass as a Bioenergy Crop,
S. McLaughlin, J. Bouton, D. Bransby, B. Conger, W. Ocumpaugh, D. Parrish, C. Taliaferro, K. Vogel, and S. Wullschleger.   www.hort.purdue.edu/newcrop/proceedings1999/v4-282.html

 

Stand Establishment

Management Guide for the Production of Switchgrass for Biomass Fuel in Southern Iowa

Prepared by Alan Teel, extension program specialist; Stephen Barnhart and Gerald Miller, extension agronomists.

www.extension.iastate.edu/Publications/PM1710.pdf

bioenergy.ornl.gov/papers/bioen98/teel.htm

Planting and Managing Switchgrass for Forage, Wildlife, and Conservation
Authors: Dale D. Wolf and David A. Fiske:
extension agronomist, forages, Virginia Tech;
extension agent, respectively, Publication Number 418-013, June 1996.

www.ext.vt.edu/pubs/forage/418-013/418-013.html

 

Costs of Producing Switchgrass for Biomass in Southern Iowa
Mike Duffy and Virginie Y. Nanhou,
Iowa State University, University Extension,
PM 1866, April 2001,
www.extension.iastate.edu/Publications/PM1866.pdf