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Publication #SS AGR 291

Production of Biofuel Crops in Florida: Switchgrass 1

Yoana Newman, Mary J. Williams, Zane Helsel, and Joao Vendramini2

Introduction

Switchgrass (Panicum virgatum) is a warm-season, perennial grass native to North America. Although commonly associated with the American tallgrass prairie, switchgrass is also part of Florida's natural ecosystem. Nationwide, numerous switchgrass cultivars have been developed for forage, but most of them do not grow well in Florida because they were developed from northern populations. The cultivars Miami, Stuart, and Alamo are recommended for Florida. Alamo was developed from a native population found at 29° north latitude in east Texas and has proven to be well adapted to the lower southeastern United States. Miami and Stuart are both Florida selections that have proved as good as or better than Alamo in field plantings throughout the state in terms of persistence and dry matter production. Miami has particularly higher production on organic soils in south Florida.

Figure 1. 

Occurrence of Switchgrass (Panicum virgatum L.) in the United States.


Credit:

http://plants.usda.gov/java/profile?symbol=PAVI2


[Click thumbnail to enlarge.]

Current Potential for Use as Biofuel

Because of its wide range of adaptation and high dry-matter production potential under low fertility conditions, switchgrass was identified by the US Department of Energy in the 1990s as a potential bioenergy feedstock. Most of the research with switchgrass has been directed toward biomass production as a combustion fuel for local space heat or to supplement coal for generation of electricity, but switchgrass is also a potential feedstock for lignocellulosic ethanol production.

Figure 2. 

Lowland type switchgrass in full flower at the USDA, NRCS, Brooksville Plant Materials Center in Brooksville, Florida.


[Click thumbnail to enlarge.]

Biology of Switchgrass

Switchgrass is an erect, warm-season perennial grass that ranges between 1.5 and 8 feet tall. It produces a flush of new tillers each spring with a high ratio of reproductive to vegetative tillers, most of which will produce a seed head under adequate moisture conditions. It is drought tolerant with a deep root system that can reach up to 10 feet in depth. The general appearance of the plant is that of a loose bunchgrass, but it has short rhizomes and stands can thicken to form a sod. Two general morphological types are recognized. The lowland type has tall, coarse stems and is adapted to poorly drained soils, while the upland type has short, fine stems and is more drought tolerant. Both upland and lowland types are found in Florida.

Production

Switchgrass has a wide range of soil adaptation, growing well in sands to clay loams with pH values of 4.5 to 7.6. In Florida, switchgrass should be planted from February–March (south and central Florida) through March–April (north Florida) with 4 to 6 lb. pure live seed/acre using a Brillion seeder or other drill at a planting depth of 1/4 inch. It grows from February/March through November, but it is photoperiod-sensitive and, as days get short, it will start flowering. If winters are mild, it may grow year-round in south Florida. To keep dry-matter production high and maintain vigorous stands, only one harvest per year in the fall is recommended. In extreme south Florida, a harvest can be made at the beginning of the dry season (late September–early October) and another harvest taken in mid- to late February just as new spring shoots are appearing. Stands should be fertilized with P, K, and micronutrients according to soil test prior to planting. No broadcast nitrogen should be applied during the establishment year to minimize weed growth. However, 20 lb./a of a slow release N can be applied near the seed if planting on low organic matter sands. In subsequent years, stands should be fertilized after spring growth begins with 80 to 100 of N plus P and K according to soil test and prior to each growth. On sands, it may be helpful to apply part of the N as the slow, release type. Stands may not reach full yield potential until the third year, particularly in the northern part of the state.

Potential Yields

Switchgrass biomass production depends on location and cultivar. In the U.S., yields from best adapted cultivars have ranged from 10,000 to 20,000 lb/acre/year. In Florida, yields range between 4,000 to 8,000 lb/acre/year under average conditions. If switchgrass is fertilized and adequate moisture is present, yields in Florida have exceeded 12,000 lb/acre/year.

Production Challenges

In Florida, less is known about switchgrass production than other biofuel crops that have been more widely studied for biomass production in the state, such as sugarcane, sweet sorghum, elephantgrass, energycane, etc. An advantage of switchgrass for biofuel production in Florida is that stands can be established from seed. Compared to most of the commonly planted pasture grasses in Florida, switchgrass stands can be hard to establish due to weed competition, too great a planting depth, and low quality or dormant seed. Regarding pests, weed control is a problem in the seeding year. Rust has been an issue in central Florida and can be a serious disease particularly in the southern part of the state during wet humid periods in the summer. Another challenge is that stand persistence and production of all commercially available switchgrass cultivars are poorer in Florida than other areas of the country. Stands may need to be renovated every 5 to 10 years to maintain commercially acceptable yield. Studies of native Florida switchgrass lines have shown that Florida material is more persistent and higher yielding than even Alamo. An additional issue associated with biofuel production, either for direct combustion or lignocellulosic ethanol production, is the moisture content of the feedstock. Even in the fall, field drying conditions in Florida are not usually favorable to decrease moisture concentration in warm-season grasses. In the case of standing switchgrass crops, field drying conditions may be an issue. To allow for drying, compromises may have to be made between maximum dry-matter yield and moisture content.

Estimated Production Costs

Switchgrass has not been commonly planted in Florida, even for forage production, so production costs are not well established. For those familiar with perennial forage grass production, it can be reasonably assumed that site preparation costs and establishment herbicide costs should be similar to those for planting warm-season perennial grasses such as bahiagrass or bermudagrass. Fertilizer costs will be similar to any crop receiving similar levels of inputs, while harvesting and transportation costs will depend on yield. The EDIS publication "Economic Potential of Switchgrass as a Biofuel Crop in Florida" (http://edis.ifas.ufl.edu/fe900) is available to evaluate the overall potential economics.

Environmental Concerns

Properly managed switchgrass stands combined with low fertility requirements suggest that long-term, widespread production of switchgrass should have little environmental impact on lands currently in improved pasture, citrus groves, or row crops. Even though switchgrass removes relatively low levels of phosphorous (5 lb./acre/year) compared to bermudagrass (~35 lb./acre/year), some positive benefit could be expected from continuous production on sites with high phosphorous levels. Switchgrass can provide several ecosystem benefits, such as erosion control, enhancement of water quality, and a wildlife habitat.

Summary

Nationwide, switchgrass is recommended for biofuel production because of its wide range of adaptation and high potential dry-matter yield with relatively low fertility input. It can be used for both lignocellulosic ethanol production and in electricity generation, complementing coal as a co-firing agent supplement. Less is known about switchgrass production in Florida than other biofuel crops.

Sources of Additional Information

Comis, D. 2006. Scientists Study Feasibility of Switchgrass for Energy. http://www.ars.usda.gov/is/pr/2006/060310.htm.

Helsel, Zane and Jose Alvarez. 2012. Economic Potential of Switchgrass as a Biofuel Crop in Florida. http://edis.ifas.ufl.edu/fe900.

Power Plant Benefits, Chariton Valley Biomass Project: Home Grown Energy. http://www.iowaswitchgrass.com/benefits~powerplantbenefits.html.

Bransby, D. Switchgrass Profile. Auburn University. http://bioenergy.ornl.gov/papers/misc/switchgrass-profile.html.

Vogel, K.P., and R.A. Masters. 1998. Developing Switchgrass into a Biomass Fuel Crop for the Midwestern USA. http://bioenergy.ornl.gov/papers/bioen98/vogel.html.

Bibliography

Cassida, K.A., J.P. Muir, M.A. Hussey, J.C. Read, B.C. Venuto, and W.R. Ocumpaugh. 2005. Component Concentrations and Yields of Switchgrass in South Central U.S. Environments. Crop Science. 45:682-692.

Moser, L.E., and K.P. Vogel. 1995. Switchgrass, Big Bluestem, and Indiangrass. pp. 409-420. R.F. Barnes, D.A. Miller, and J.C. Nelson (eds). Forages Vol. 1, An Introduction to Grassland Agriculture. Iowa State Univ. Press, Ames.

Muir, J.P., M.A. Sanderson, W.R. Ocumpaugh, R.M. Jones, and R.L. Reed. 2001. Biomass Production of 'Alamo' Switchgrass in Response to Nitrogen, Phosphorous, and Row Spacing. Agronomy Journal. 93:896-901.

Pfaff, S. 1999. Belleview Perry Sprayfield - Plant Materials Adaptation Report, 1998 Annual Report. USDA, NRCS Brooksville Plant Material Center. 31 p. http://www.plant-materials.nrcs.usda.gov/pubs/flpmcbr5447.pdf.

Sanderson, M.A, J.C. Read, and R.L. Reed. 1999. Harvest Management of Switchgrass for Biomass Feedstock and Forage Production. Agronomy Journal. 91:5-10.

Vogel, K.P. 2004. Switchgrass. pp. 561-588. In L.E. Moser, B.L. Burson, and L.E. Sollenberger (eds). Warm-season (C4) grasses. ASA, CSSA, SSSA publishers.

Footnotes

1.

This document is SS AGR 291, one of a series of the Agronomy Department, UF/IFAS Extension. Original publication date January 2008. Revised March 2014. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Yoana Newman, assistant professor, Agronomy Department; (Curtis Rainbolt, author on first edition and former assistant professor, Agronomy Department, Everglades Research and Education Center, Belle Glade, FL); Mary J. Williams, Florida USDA NRCS, Ecological Science Section, Plant Material Specialist; Zane Helsel, professor, Department of Plant Biology and Pathology, Rutgers University, NJ, and courtesy professor, Agronomy Department, UF/IFAS Extension; and Joao Vendramini, assistant professor, Agronomy Department, Range Cattle Research and Education Center, Ona, FL; UF/IFAS Extension, Gainesville, FL 32611.


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U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.