Mulling over prospects for growing switchgrass as a feedstock for biofuel or biopower? In many respects, it's not all that much different from growing other forage crops.
“All of the basics still apply,” says University of Kentucky forage specialist Ray Smith. He's working with 20 farmers in a four-year-long project to grow switchgrass for generating electricity at a power plant in eastern Kentucky.
“You still have to do a good job of matching varieties to soil types, determining seeding rates, controlling weeds and harvesting in a timely manner.
“The main difference is that with crops like alfalfa or fescue, you can often vary a little from what's recommended and still end up having success,” Smith adds. “With switchgrass, though, you don't have much latitude for making mistakes. You pretty much have to follow all of the recommendations to the letter.”
Consider the following before deciding whether switchgrass is for you:
Successfully establishing a productive switchgrass stand requires patience. In the Kentucky project, nearly a third of the 20, 5-acre plots planted during 2007 and 2008 failed and had to be replanted. New stands will need at least three years to reach full yield potential.
“There are exceptions,” Smith says. “Some growers we've worked with have seen good yields in the first year. But if you're working up a budget, you'll probably want to figure on getting one-third of a full yield during the establishment year and two-thirds of a full yield in year two. If you've grown switchgrass and are optimistic, you might bump that up to one-half of a full yield during the first year and three-fourths in the second year.”
Ken Goddard, an extension specialist with the University of Tennessee's Biofuels Initiative, says weed competition is the biggest hurdle to get stands established.
“One of the major problems growers face right now is that, in many states, there aren't a lot of postemergence grass herbicides registered for use on switchgrass,” he says. His advice: Don't plant switchgrass on fields with histories of heavy annual signalgrass or broadleaf weed infestations.
Other practices that can help battle weeds: applying a preplant burndown, planting at shallow depths (to help germination) and mowing/clipping when chemical weed control is not available.
For established stands, Gary Kelderman, who has grown switchgrass on his Oskaloosa, IA, farm since 2002, says controlled burning a few weeks before spring planting is also effective.
“A controlled burn is a duplication of the lightning strikes and natural fires that have kept native prairies so productive for centuries,” says Kelderman. He grows 350 acres of switchgrass as part of a project geared toward eventually producing biomass for an Iowa electrical plant. “Along with controlling weeds, burning also helps with germination. The fire cracks the tough coating on the seeds that dropped to the ground during the previous year's harvest. It helps thicken stands.”
“During the establishment year, we recommend you don't apply any nitrogen,” says Goddard. “It just encourages more competition from weeds.”
In the second and subsequent years of a stand, use soil tests to determine N application rates. For P and K, Goddard recommends foregoing fertilizer application if soil tests are at medium to high levels. If soil tests are low for phosphorus, add 40 lbs; if low for potash, add 80 lbs.
Over the last 20 years or so, there hasn't been much market incentive for seed companies to develop new, high-yielding switchgrass varieties. But with potential new energy uses, that's likely to change (see “Dedicated Energy Crop Seed Released,” page 36).
Iowa grower Kelderman expects more variety introductions soon. “We're at the same point now with switchgrass genetics that we were at with corn genetics in the 1950s or 1960s,” he says. “Within five or six years, I think we'll have varieties that will produce 5 tons/acre on ground with a CSR (Corn Suitability Rating) of 50-60. In 10 years, we'll see varieties capable of producing 10 tons on ground with a CSR of 75-80.”
By comparison, the average yield for the first stands of Cave-In-Rock switchgrass Kelderman planted in 2002 is now around 2.5-3 tons/acre. Some of those stands have yielded more than 6.5 tons/acre.
While researchers and growers involved in switchgrass production projects report paying as much as $30/lb for seed, Kentucky's Ray Smith says $10/lb is a more realistic figure to use for budgeting purposes. For seeding rates, he figures 6 lbs/acre. He notes that with alfalfa, typical seed cost is roughly $4/lb and seeding rates are around 20 lbs/acre. “It's really not that much of a difference,” he says.
Kelderman pays $8-12/lb for switchgrass seed and seeds around 8 lbs/acre. “With alfalfa, you might get six years out of a stand,” he says. “In our area, we've harvested switchgrass fields that are more than 20 years old. And once switchgrass gets established, you don't have much in the way of input costs to keep it going.”
Because biofuel/biopower production requires dry material for processing, switchgrass grown for those purposes is typically harvested once a year after a killing frost. Harvesting dry material requires adjustments, says Tennessee farmer Tim Brannon, who planted 15 acres of switchgrass in 2005 as part of a University of Tennessee pilot project for producing electricity.
“We had some problems at first with the stubble puncturing tires on equipment,” says Brannon, who also owns ag implement dealerships in Paris, TN, and Hopkinsville, KY. “The stems can be extremely tough. After cutting with a disc mower, you end up with little pongee sticks.”
Adjusting cutting height to a minimum of 6” was his solution. “That way, the tires push the stubble over as you go along.” Brannon also notes that, because switchgrass can grow to a height of 6-7', cutting with a disc mower and conditioner can be challenging.
“It wasn't really a problem the first couple of years because there wasn't a lot of grass there,” he says. “But once the crop is established, the grass would lean over and lodge in front of the mower. Last year, we used a New Idea 279 Cut/ditioner with swinging flail blades and that worked a lot better.”
Bottom line, Brannon says, growers set up with high-capacity forage harvesting equipment won't have many problems handling switchgrass.
“If you don't have the equipment to handle this kind of crop mass though, you probably should consider hiring a custom harvester to do the job for you,” he says.