Research by scientists at The Samuel Roberts Noble Foundation continues to reveal vital information about establishing switchgrass as a bioenergy crop in Oklahoma.

"Switchgrass is a native range and pasture grass that has been identified by state and national leaders as a potential crop to be grown, harvested and converted into ethanol," said John Guretzky, Research Agronomist at the Noble Foundation. "Slow seedling establishment has previously limited the adoption of switchgrass in forage production. However, the Noble Foundation's research is providing valuable insight into the proper methods of establishing and producing switchgrass."

Currently, two switchgrass types are available for planting - lowlands and uplands - each type being particularly suited to different climates and soils. Lowland types, such as those used in Oklahoma, tend to grow taller and more rapidly than upland types. Despite which type of switchgrass is selected, Guretzky said a grower must be careful when buying seed.

"When choosing a variety, it is important to purchase high-quality, certified seed," he said. "Check with seed companies on availability and quality of their seed before making purchases."

Selecting the best seed is just the beginning. According to Noble Foundation research, switchgrass must be planted properly to increase chances of stand establishment. The best time to plant switchgrass in Oklahoma is spring. Switchgrass seedling growth is best when air temperatures reach 75 to 85 degrees.

Planting methods for switchgrass include drilling or broadcasting (techniques where seed is spread uniformly across the soil surface) into either tilled or no-tilled seedbeds. Drilling involves planting in rows using either a conventional or no-till drill, Guretzky said.

"Regardless of the method used, switchgrass should be planted at shallow depths of 0.25 to 0.5 inches," Guretzky said. "It should be planted in seedbeds that are firm enough to allow good seed-to-soil contact, but not so firm as to restrict root growth."

Research shows that switchgrass produces similar yields across a range of seeding rates and row spacing. At lower plant population densities, individual plants are able to exploit more space and soil resources, attain greater size and maintain biomass yields equivalent to those grown at higher plant population densities, Guretzky said. He recommended seeding rates of switchgrass of 4 pounds of pure live seed per acre with higher rates applied to sites with historically poorer growing conditions.

"When planting switchgrass, do not apply nitrogen fertilizer because switchgrass seedlings grow slowly and nitrogen fertilizer favors the growth of weeds over that of switchgrass," Guretzky said. "Nitrogen fertilizer can be used when switchgrass is fully established. Fifty to 100 pounds of nitrogen per acre typically maximize biomass yields of fully established stands."

Although there are no proven weed control methods that consistently allow switchgrass stand development, the best form of weed control is to delay planting until "grassy" weeds emerge so they can be sprayed with glyphosate before planting switchgrass, Guretzky said.

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News Release Issued: July 27, 2007

The Samuel Roberts Noble Foundation, Inc. (www.noble.org), headquartered in Ardmore, Okla., is a nonprofit organization conducting agricultural, forage improvement and plant biology research; assisting farmers and ranchers through educational and consultative agricultural programs; and providing grants to nonprofit charitable, educational and health organizations.