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Switchgrass Breeding Lifecycle - Early Findings

"Switchgrass breeding is in its infancy" according to Dr. Stacy Bonos, Associate Professor in the Plant Biology and Pathology DepartStacy Bonosment at Rutgers University. "The big question is economics for the landowner; right now, switchgrass competitors [such as hay] provide more profitsper ton. However, the prospect of a sustainable energy market moves closer to reality every day." Bonos (photo at right) shared developments in switchgrass production in a NEWBio webinar on March 11 (recorded webinar here).

Switchgrass (Panicum virgatum) has been bred since the 1970s, but breeding specifically for biofuel did not start for another twenty years. Switchgrass domestication and optimal cultivar development research point to its increasing marketability as an energy crop.

A number of factors come into play, among them low maintenance costs during its three-year establishment period and carbon sequestration capabilities that help counter carbon emissions. Bonos shares some of her findings to date on each stage the switchgrass lifecycle.

On paper, switchgrass seedlings can be planted on a variety of land types with a range of pH values. Upland switchgrass should be planted on drier land, while lowland switchgrass should be planted on wetter land. Both types need to be planted in such a way that their roots become deeply embedded in the ground; otherwise, the switchgrass will succumb to adverse weather conditions, such as drought. Planting usually takes place in late spring.

Although marginal lands, such as reclaimed mine sites, are generally said to be suitable for planting and growth of switchgrass, findings by NEWBio researchers have identified a few challenges. Bonos has been studying the growth ability of switchgrass and found "significant reductions in yields on marginal soils…is it worth it for a farmer to plant switchgrass on marginal land and only reap one ton per acre?" Over 150,000 acres of reclaimed mine sites in West Virginia will be well utilized if planting switchgrass on marginal land can be proven cost-effective.

Bergstrom anthracnose imagePost-planting, switchgrass takes three years to mature and faces two main hurdles before harvesting: Weeds and Anthracnose disease. Bonos has NEWBio switchgrass trials underway in three New Jersey locations: Freehold (prime land), Jackson (marginal land), and Somerset (marginal land). "Weed pressure in Somerset was excessive...it took two years before the switchgrass was the predominant species", described Bonos. Weeds germinate much faster than switchgrass, and need to be removed from the site very early. Mowing is most widely used as weed controlled, followed by herbicides. Anthracnose (left, image credit: G. Bergstrom, Cornell University) causes foliar lesions, and is seen as a barrier for high yields of some switchgrass ecotypes. One of Bonos' NEWBio goals is to determine the extent of damage that can be caused by this disease.

Harvesting of switchgrass can take place in the fall or spring, with both times having advantages and disadvantages. First-frost harvesting allows for maximum yields, which is necessary when working towards maximum cost-effectiveness. Spring harvesting can reduce yields up to 30%, but allows for maximum nutrient recycling and provides habitat for small mammals during cold conditions. Conventional mowing and bailing equipment can be used to harvest switchgrass, which can then be used as a clean transportation fuel or heating fuel.

Contributed by Rachel Passmore, Penn State Class of 2014 and NEWBio Intern. Acknowledgements to Dr. Stacy Bonos, Penn State Extension, and West Virginia Extension

NEWBio (consortium members below) is supported by Agriculture and Food Research Initiative Competitive Grant no. 2012-68005-19703 
from the USDA National Institute of Food and Agriculture.
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