Switchgrass provides crop option for drylands farmers, creates haying, grazing and biofuel opportunitiesWritten by Gayle Smith
Every farmer can think of areas of marginal cropland that are difficult to farm. With farm equipment getting larger, more and more of these areas are cropping up. Rob Mitchell, a research agronomist with the USDA Agricultural Research Service, suggests planting these areas to switchgrass.
Switchgrass is a perennial grass that is native to North America. It is a good choice for poorly productive fields, difficult to farm areas or pivot corners, according to Mitchell.
“Switchgrass can be very productive on marginal cropland. If we can grow a dryland crop at all on that site, it will work for switchgrass,” he says.
The crop can become very productive very quickly. Once its established, current research indicates at least a 10-year life cycle.
“It will reach 50 percent of its yield by the end of the first growing season, and by the end of the second growing season, it should be at 100 percent,” he noted.
Switchgrass research has been ongoing in Nebraska since 1936.
Planting and grazing
Farmers plant the crop for a variety of reasons, but mostly for hay, forage and conservation purposes. Many farmers choose it to plant their Conservation Reserve Program (CRP). Mitchell said the cost to produce switchgrass depends on yield, but a general rule of thumb is a yield of six tons of biomass per acre. At an average of $60 an acre, the better the yield, the more profitable the crop is.
If farmers chose to hay or graze the crop, Mitchell warns against feeding it to horses.
“Switchgrass contains diosgenin, a chemical that is toxic to horses and other non-ruminants. It can kill them,” he says.
Research is underway to determine if levels of diosgenin decline with plant height or as the growing season progresses.
Researchers also continue to study the feasibility of growing the crop as a potential biofuel.
“Switchgrasses and perennial grasses as sources of bioenergy and fuel are a pretty natural fit,” Mitchell says. “These grasses are not only good for livestock but are also good for ethanol and other biofuels.”
He continues, “If this whole concept of bioenergy comes, it is good to have options. It gives us some flexibility in how we will market these perennial grasses, whether it is through livestock or a stationary fermenter. The concern is that it will take a large number of acres if this concept is ever developed to operate a biofuel plant.”
If these plants ever come online, they will require a lot of material. Mitchell says with current technology, switchgrass and other perennial grasses are capable of producing 80 gallons of ethanol per ton.
“If we do the math, they would require 625,000 tons of biomass per year for a 50 million gallon plant,” he explains.
Ideally, the perennial grasses would have to be grown within 25 miles of the plant to be economically feasible.
“It will be a very intense and localized area. If switchgrass only yields a ton to the acre, it would take half the land within as 25-mile radius to make the plant work,” he says. “That doesn’t make much sense.”
Instead, researchers are continuing to work on developing varieties that consistently produce better yields to cut back on the amount of acreage needed.
Switchgrass yields are dependent on precipitation, fertility, soil, location and genetics. Mitchell encourages farmers not to fertilize the crop the year it is planted but to wait until the second year when fertilizer will be needed.
For switchgrass to bioenergy to become a reality, Mitchell says a consistent supply must be developed, since these plants operate 365 days a year. Farmers must also do a good job putting up the grass as hay, since the bales may have to be stored for long periods of time until the plant can utilize them.
“There are also numerous environmental benefits to switchgrass that can improve agricultural land use practices, such as stabilizing soil and reducing soil erosion, improved water quality, increased and improved wildlife habitat and storing carbon to mitigate greenhouse gas emissions,” he explained.