Switching to Switchgrass Makes Sense

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Switching to Switchgrass Makes Sense joint feasibility study by the U.S. Departments of Agri- culture and Energy says that relief from soaring prices at the gas pump could come in the form of plants like the native prairie grass called switchgrass (Panicum virgatum). Plant-based biofuels, such as ethanol, significantly reduce net emissions of greenhouse gases compared to petroleum-based fuels.

The plants grown for biofuels also store carbon in soil, which acts to mitigate the effects of industrial greenhouse gas emissions. Switchgrass has one of the highest potentials for use as a biofuel crop in the United States, mainly because it grows well under a wide range of conditions. It 9s a perennial, so after establishment, it doesn 9t require an- nual tillage.

This increases soil carbon at the surface, and reduces losses of soil, water, and fertilizer. It also provides excellent habitat for pheasants, ducks, and other wildlife. Switchgrass is high-yielding over much of the country 4from 7 to 16 tons an acre in the Southeast, to 5 to 6 tons in the west- ern Corn Belt, to 1 to 4 tons in North Dakota.

Each ton of dry switchgrass might yield as much as 96 gallons of ethanol. Switchgrass could be economical ... more. less.

with other crops, especially in the Northern Plains, and reduce U.S. dependence on foreign oil. It could also have the added advantage of helping to build a bioenergy industry in remote areas, thereby boosting rural economies. This native perennial has been shown to store more soil carbon than the major U.S. farm crops. A study by soil scientist Mark Liebig, rangeland scientist Holly Johnson, and colleagues at the ARS Northern Great Plains Research Laboratory in Mandan, North Dakota, explained how. They found that switchgrass stores most of its carbon deep underground. While previous studies only measured carbon retained in the top foot of soil, Liebig and Johnson sampled 4 feet beneath fields of switchgrass, corn, and wheat on 42 farms in North Dakota, South Dakota, and Minnesota. The researchers found that switchgrass fields had much more soil carbon than nearby corn and wheat fields 4about 7 tons more per acre, on average. This was true at all depths, but the advantage was most pronounced at 1 to 3 feet below the soil surface. And according to Liebig, cthe deeper you store carbon, the less chance of its returning to the atmosphere as carbon dioxide. d The reason for this depth advantage lies in the fact that switch- grass has an extensive root system 4with some roots as long as 8 feet 4so much of the plant 9s carbon is in its roots and the belowground crown tissue just above them. cThe sites we studied are representative of about 74 million acres of the Northern Plains and northern Corn Belt, d Liebig says. cNext, we need to conduct similar studies in other regions to better understand the quantity and depth distribution of carbon stored by switchgrass and see whether this deep carbon storage holds true elsewhere. d There are plans to evaluate switchgrass at the Henry A. Wallace Beltsville (Maryland) Agricultural Re- search Center. 4By Don Comis, ARS. This research is part of Bioenergy and Energy Alternatives, an ARS National Program (#307) described on the World Wide Web at www.nps.ars.usda.gov. Mark A. Liebig is with the USDA-ARS Northern Great Plains Research Laboratory, 1701 10th Ave., S.W., Mandan, ND 58554-0459; phone (701) 667-3079, fax (701) 667-3054, e-mail liebigm@mandan.ars.usda.gov. 8 A Switchgrass, Panicum virgatum. JOHN BERDAHL (D551-1) This deep-rooted carbon-storing perennial has great biofuel production potential 19 Agricultural Research/July 2006 400730 19 6/1/06 7:55:16 AM

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