Reduced-lignin crop may offer harvest flexibility, other benefits
Reduced-lignin alfalfa can be harvested eight to 10 days later than conventional alfalfa while maintaining its quality. That may mean fewer cuttings per year, saved labor, machinery and fuel costs and, believes Dan Undersander, increased yield.
Undersander, extension forage specialist with the University of Wisconsin, conducted field trials of two experimental transgenic alfalfas with reduced amounts of lignin.
“Because of the reduced lignin, we were able to delay harvest eight to 10 days and get the same quality forage. It means you've got a wider harvest window. If you're in an area with a four-cut system, you can back off to maybe three cuts,” he says.
“One thing you see in the Midwest is, if you miss your cutting by five days, you go from dairy-quality forage to beef-quality forage on your entire field. But if this alfalfa holds quality for another eight days, then you have a little flexibility when you cut.”
Lignin is needed in plants to hold them upright, yet it also lowers digestibility. Down-regulating or lowering the activity level of enzymes that control lignin results in lower amounts of lignin. Alfalfas bred with the reduced-lignin trait have up to 10% greater fiber digestibility when fed to cows and lambs.
Recent feeding trials using the genetically modified alfalfa were conducted by Dave Mertens, U.S. Dairy Forage Research Center, Madison, WI, and David Weakley, LongView Animal Nutrition Center, Gray Summit, MO.
They determined that the animals digested an additional 10% of the feed's fiber and excreted less manure. That, of course, could increase milk production or provide the same amount of milk with less feed, Mertens suggested. (See “Highly Digestible Feed,” page 19, in Hay & Forage Grower's May issue.)
One of the two tested alfalfas showed good standability, Undersander says. “One doesn't stand up quite as well, and that's probably not the one we'll be going forward with.”
The fate of this transgenic alfalfa may rest with that of Roundup Ready alfalfa, according to industry sources. If Roundup Ready alfalfa is again deregulated, reduced-lignin alfalfa could be available to growers by 2014 or 2015, according to Forage Genetics, which partnered with the U.S. Dairy Forage Research Center and the Noble Foundation to develop the alfalfa.
The field trials were planted at Becker, MN, and West Salem and Arlington, WI, a year ago last spring. “Last year we cut them all uniformly once about the middle of June. Then we cut them every five days for five or six time periods after that so we could look at the yield and quality of each plant over time.”
Undersander estimates up to a 30% yield increase with reduced-lignin alfalfa. He's basing that on a previous study comparing yields of three-cut vs. four-cut systems harvested by Sept. 1.
“Over three years, the average yield increase from a three-cut system was 32% more than from a four-cut system. If you think about it, the reason is that the alfalfa's got more leaf area in the summer instead of being cut back one extra time and having to start over. So it looks to us like this will be an outstanding way to both reduce the labor and to increase yield.”