Get the lowdown on reduced-lignin alfalfa

Carol Spaeth-Bauer
Wisconsin State Farmer
Reduced-lignin alfalfa varieties provide farmers with more options in variety types and how they are used.

There hasn't been a lot to get excited about when it comes to alfalfa quality, that is not until reduced-lignin alfalfa entered the scene. Now it's a whole new ball game, giving farmers more options. 

Farmers can choose between conventionally developed reduced-lignin, high digestibility alfalfa varieties or HarvXtra. They can harvest at the bud stage or at early bloom. Farmers can also choose to seed with or without a forage grass. 

"It's great to have options," said agronomist Ev Thomas, Oak Point Agronomics president. "We have options in variety types and in how we use these varieties."

Improvements in alfalfa yield and quality have been slow in coming for many years, Thomas said during a Hoard's Dairyman webinar on reduced-lignin alfalfa. Until recently, many of the biggest genetic improvements in alfalfa have been in disease resistance. 

"However, unless a disease is present, we don't see a big impact on performance or quality," Thomas pointed out. "As we get into the new era, with reduced-lignin alfalfa or high digestibility alfalfa ... this is going to be a real game changer. I think it's the most significant improvement in forage quality in many years."

Previously, many improvements in quality were achieved by more intensive harvest management, "but that was self-limiting," because once harvesting is done before the bud stage, there's impact on yield and stand longevity. Farmers were feeling like they had "pushed intensive harvest management just about as far as they can go," Thomas said. 

Reduced-lignin alfalfa varieties should result in improved forage quality, along with possible increased yield and stand longevity, depending on harvest timing. 

Improving forage quality

Among the alfalfa varieties touting improved forage quality are the genetically modified HarvXtra, which include both the Roundup Ready trait and the trait resulting in significantly reduced lignin content. 

Conventionally-bred alfalfa varieties, such as Hi-Gest and Kingfisher 425HD, are promoted as having reduced lignin content and/or higher digestibility. Kingfisher 425HD was bred for higher than normal digestibility, but has a normal lignin content, whereas, Hi-Gest was bred for lower lignin. 

The new era of alfalfa varieties, which includes high digestibility alfalfa, is going to be a game changer for farmers.

When comparing varieties in university trials, HarvXtra has twice as much decrease in lignin —14 percent less — as increase in fiber digestibility — 7 percent. Hi-Gest had the same decrease in lignin, as the increase in fiber digestibility. 

In the 2017 World Forage Analysis Superbowl, comparing crude protein in three categories — conventional varieties, high quality varieties and HarvXtra — high quality varieties were a percent higher than conventional alfalfa varieties and HarvXtra picked up several more points.

"You can see we are stepping up in digestibility," Thomas said. 

Harvest options

Thomas believes harvest options are going to be "quite important" since reduced-lignin alfalfa offers more options than conventional varieties. 

One option is to harvest at the bud stage, "what most farmers are doing anyway." 

"This will result in very high crude protein and very high fiber digestibility," Thomas explained. "In some cases, perhaps higher than farmers are used to in the past."

It also gives farmers a "little longer harvest window," from a few days to as much as 10 days depending on variety, for "when things happen that you don't intend to happen." 

Forage quality is going to remain higher since reduced-lignin varieties have significantly lower levels of lignin at any stage of bloom. "That's the advantage," Thomas pointed out. 

The other harvest option being recommended with reduced-lignin alfalfa is to delay harvest seven to 10 days to about 10 percent bloom. Delaying harvest can provide higher root carbohydrates, with less labor and less harvest cost, according to Thomas. 

Delaying alfalfa harvest to about 10 percent bloom with reduced-lignin varieties, not only can provide higher root carbohydrates, but can also reduce crown damage from field traffic.

Harvesting at bud stage never allows the alfalfa to fully recover carbohydrates, which would require getting close to full bloom, even with reduced-lignin alfalfa. Delaying harvest seven to 10 days gets closer to the ideal, "and that's important," said Thomas. 

Another advantage to delaying harvest, one that is sometimes underestimated, is less crown damage from field traffic.Thomas said an agronomist from Cornell University estimated, by the time a farmer harvests alfalfa three times, every plant in the field has been run over at least once.

"I’ve dug a lot of alfalfa plants out of three- and four-year-old fields and it's amazing how much crown damage some of these plants have and continue to live — but live and live well may be different things — especially as we get into the third and fourth year," said Thomas. "I think the result of one or less cuttings per season — the advantages may start to accumulate and we may start to see considerably healthier stands in the last couple of years of stand life."

In addition to having fewer harvests, there might be higher annual yields, along with the cost savings from one less harvest. 

"As we start to impose this type of management on reduced lignin alfalfa, maybe we’re going to get 15 to 20 percent higher yield while still maintaining higher forage quality and that’s a win-win situation," Thomas added.

Harvesting can also be varied from cut to cut, maybe taking one cut at bud stage and delay another. "There are all kinds of options," Thomas added, providing "several harvest management systems that are possible and they can be tailored to the needs of each dairy farm."

Reduced-lignin alfalfa with grass

There is a lot of alfalfa grown with forage grass in farms in the northeast U.S. or north central or eastern half of Canada, according to Thomas.

Thomas said grass can be seeded with reduced-lignin alfalfa just as it would with conventional varieties, however, it's not recommended to delay harvest because the grass would be too mature by then. 

"I think seeding grass with reduced-lignin alfalfa gives us a really good option as long as we are going to be harvesting in the bud stage," said Thomas. "That's different with HarvXtra."

Since HarvXtra is Roundup Ready, farmers have paid for that trait, "so why not use it." 

"But if they use alfalfa grass and they apply glyphosate it's’ going to kill the grass, so there is a limitation," Thomas said. "Some farmers have achieved success by seeding grass one to seven days after glyphosate was applied."

Thomas is optimistic that "farmers will figure out a way to get it done," if they want to use grass and HarvXtra. 

Research data is limited so far on reduced-lignin alfalfa, but more research is on the way.

"Reduced lignin alfalfa is new stuff. We need to be patient. We’re still learning how to best use this exciting new technology," said Thomas. "I think in a year or two we’re going to be a lot smarter than we are now because we’re going to have more research under our belt."

Yes, genetically modified HarvXtra is "considerably more expensive," but with proper management, "increased milk production from higher forage quality, and possibly higher yield, should more than compensate for higher seed cost," Thomas said. "Seed cost, even with fairly expensive seed, is a rather small portion of the total investment in alfalfa production."