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How Green is Switchgrass Farming?

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The rolling foothills of the Southern Appalachian Mountains resting in hazy azure against a golden-green field could make anyone want to be a farmer.  Up close to the five-feet-tall stands not yet harvested, the wispy tops  bowing in a slight breeze, one can imagine great expanses of this native plant.
Today’s resurgence of switchgrass in the Southeastern United States has nothing to do with nostalgia.  When hundreds of people recently gathered in a switchgrass field for a biomass field day, they wanted to learn about production and profits.

Efficient production typically begins with a chemical burn of glyphosate or other weed killer before switchgrass is planted.  Because the plant is slow growing, spending most of its effort the first year taking root, other plants can easily overtake it.  What an ecologist might call native or nonnative plants, a farmer calls weeds.  University of Tennessee Plant Scientist Neil Rhodes emphasized that without chemical weed control, a young crop of switchgrass can turn into what he calls “complete failure.”  Rhodes and other researchers keep a long list of herbicides that can be used prior to switchgrass planting.  The list includes some chemicals only allowed for crops destined to be biofuels.

With the chemical burn approach apparently the standard, I asked scientist Elizabeth Doxon about the impact on wildlife.  Doxon, with the UT Department of Forestry, Wildlife & Fisheries, said that switchgrass farmers are still managing at least some farmland for wildlife habitat.  She admitted that herbicide use is not entirely compatible with an ecological approach.  “That’s one part that we actually do struggle with,” Doxon said, “We don’t prefer herbicides because a lot of those weeds are actually great for wildlife. They can provide food, provide a lot of shelter, protection from predators. So yeah, there’s a little bit of give and take there. What we usually recommend is you might spray a certain area but not spray other areas, so it goes back to providing those different types of habitats. We don’t want to do it 100%, but maybe do it 50%, so we still have some mixture there.”

Once a stand of switchgrass has taken root, farmers are less likely to use herbicides on this cash crop.  The hardy plant can self-seed and continue growing each warm season for up to a decade.  When I asked host farmer Brad Black about herbicide use, he said it’s virtually nonexistent after the first or second year.  “These fields have not been sprayed at all the last two years.  It grows so fast it’ll choke out the broadleaf weeds.”  This is consistent with what Rhodes explained in his field day talk, “Once it’s established, we really don’t have to do much on weed control.”  Researchers say it’s easier to convert conventional row crop fields to switchgrass than it is to convert pastures.  They avoid fields where Bermuda grass has already taken hold, because even chemical weed killers can’t get rid of it.

Growers involved or interested in biomass production seem to accept herbicide use as the norm.  They also see the benefits in genetic modification of seedstock that might increase productivity through greater crop yields.

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