Reduced Lignin Alfalfa

New varieties offer increased forage efficiency.

By Des Keller | Photos By David Bagley

Forage producers can now choose between multiple types of alfalfa that are advertised as having reduced amounts of lignin in the cell walls. Introduced widely in 2017, the new alfalfa varieties, developed through traditional breeding and genetic modification, may allow producers to harvest more high-quality hay by lengthening the window of the season during which they can cut.

While lignin is an essential component to the strength and health of the alfalfa plant, it is indigestible to cows. Thus, less lignin means better digestibility for livestock.

There has always been an inherent dilemma of trying to balance alfalfa yield with forage quality—as yield increases, the digestibility of alfalfa decreases because, as the plant matures, the amount of lignin content in the stems increases.

The Lowdown on Reduced Lignin. Reduced-lignin alfalfa seeks to decrease lignin-induced indigestibility as the season progresses. In some cases, reduced-lignin alfalfa may also extend the growing season or save farmers money by decreasing the number of alfalfa cuttings needed.

Lignin constitutes 6 to 9% of the dry weight of the whole alfalfa plant and about 20% of the cell wall, says Craig Sheaffer, professor of agronomy and plant genetics at the University of Minnesota. “Lignin in a plant acts like girders do holding up skyscrapers,” he explains. There is, therefore, some concern that lodging in these new varieties could occur, although small-lot tests, says Shaeffer, have not shown there to be “any more lodging than occurs with conventional varieties.”

To be on the safe side, Sheaffer and others suggest that growers not wait for the first cutting. “Do not delay the first cutting, because the plant tends to grow too tall and can lodge,” says Dan Undersander, forage agronomist at the University of Wisconsin-Madison. “This is true of the first cutting for conventional alfalfa as well.”

Most prominent in the market is the transgenic reduced-lignin alfalfa, HarvXtra, developed in a cooperative effort between Forage Genetics International, the Noble Research Institute and the U.S. Dairy Forage Research Center. Field trials thus far indicate HarvXtra contains 12 to 18% less lignin than a typical alfalfa variety.

Additionally, HarvXtra field trials showed a 16% increase in relative forage quality during a typical harvest schedule, or up to 26% yield increase over stand life by delaying harvest intervals.

Two additional reduced-lignin varieties created via traditional breeding are Hi-Gest, released by Alforex Seeds, and 54Q14, out from DuPont Pioneer. Hi-Gest alfalfa reportedly has 7 to 10% less lignin than conventional varieties, while 54Q14 reportedly contains about 5% less lignin.

The germplasm from all three reduced-lignin versions has now been incorporated in multiple varieties within those companies—and even across the industry. For example, some DuPont Pioneer alfalfa varieties use the HarvXtra technology. However, there is no data available collected by independent third parties that directly compares the varieties developed from the two technologies.

Harvest Flexibility. These new varieties may allow about a seven-day delay (from 28 to 35 days) in harvest. The result will be greater tonnage yields due to the extra growing time, without a drop-off in forage quality. It is, however, still important to take care during harvest to minimize the loss of leaves—which have considerably less lignin than stems, according to Undersander.

Standing alfalfa, before mowing, is generally half leaves and half stems, Undersander explains. Growers should do what they can to minimize moving the forage after that—and to handle the cut crop when slightly damp or dew-covered. “The leaves dry first and fall off when the crop is dry and moved,” says Undersander, no matter the lignin content of the plant.

Both Sheaffer and Undersander say it is possible that growers could reduce by one the number of cuttings needed with reduced-lignin alfalfa, by increasing the time between cuttings after the first harvest. More likely, according to Undersander, is that growers will take the same number of cuttings, yet increase yield by using more of the growing season.

For example, Undersander says that in the Madison, Wisconsin, area, a typical cutting schedule would begin on May 20 with subsequent cuttings at 28-day intervals—June 17, July 15 and August 12.

“But alfalfa could grow until September 1 or 2,” says Undersander, “so three weeks of the growing season are not used. But with HarvXtra extending each cutting after the first by a week, we can use the full growing season and increase yield.”

The premium price of the seed would, however, need to be balanced against the price a grower could earn for higher-quality or more hay. One U.S. producer says he pays around $3 per pound for conventional alfalfa seed and about $8 per pound for Roundup Ready seed. In contrast, a transgenic alfalfa, like HarvXtra, might cost about $12 per pound. The cost-benefit is expected to be better understood after data from the 2017 harvest is recorded and analyzed.

As with all new technology, farmers should consider comparing the new technology with current varieties in a small on-farm evaluation. This will allow a trial with the management system, soil and climate..