Low lignin alfalfa provides benefits in added flexibility for producers
As alfalfa producers select their seed variety when they replant their fields, Tom Miles of Alforex Seeds notes some special consideration should be given when planting and harvesting alfalfa.
“Research has identified that as alfalfa matures, quality goes down,” Miles says. “As stems mature, they accumulate high concentration of cell wall material – lignin, and the degradability of the stems decreases as alfalfa matures. Then, quality goes down.”
At the same time, as the plant matures, the ratio of leaves to stems decreases because stem material accumulates faster than the leaf.
“Immature alfalfa, from pre-bud to bud, has a 60-to-40 leaf-to-stem ratio,” he adds. he adds. “In Arizona and California, some varieties get cut 10 to 12 times, at 18, 20 or 21 days. At full maturity, alfalfa is 40 percent leaves and 60 percent stems.”
Miles continues, “With increasing plant maturity, stems become 30 to 40 percent less digestible due to increased lignin content.”
Lignin content negatively impacts digestibility of the forage as it reduces the rate and extent of fiber digestion.
However, use of low-lignin varieties of alfalfa also bring questions and concerns.
Miles notes that, traditionally, alfalfa harvest is targeted at the point when alfalfa maturity provides the most product while also capturing the highest yield. Traditionally, that occurs at day 28 of growth, when approximately 10 percent of the plant has bloomed.
“If we harvest after day 28, with conventional alfalfa, we see quality go down while yield goes up,” he says. “Low-lignin varieties tend to hold onto their quality a little bit longer.”
If weather hits or a few extra days of growth are desired, Miles says the low lignin varieties can continue to gain in yield while maintaining quality much longer than conventional varieties.
“Harvest flexibility allows production of dairy and high-quality hay that tests better than conventional yields when they are cut at the same time,” he says. “If we want to change our cutting schedule, we can get the same yield without sacrificing forage quality.”
A second benefit of using low-lignin alfalfa, Miles explains, is to allow more time between cutting to decrease plant stress.
“Cutting the plant more frequently can decrease the life of our stand,” Miles says, “so particularly in areas where they are cutting frequently, increasing the time between cuttings has the potential for increasing stand life.”
At the same time, producers may be even able to decrease the number of cuttings and increase yield and quality of those cuttings.
When alfalfa is growing, the first 10 to 12 inches of growth is fueled by the carbohydrates stored in the root reserves of the plan.
“After alfalfa reaches 12 inches, it starts putting reserves back into the roots,” he says. “If we cut before the 10 percent bloom on a regular basis, we start to deplete some root reserves, which affects the next cutting. Delaying harvest allows us to replenish some root reserves.”
Overall, Miles says low-lignin advantages occur at mid- to late-maturation, allowing early cutting to be extended a few days, which improves yield and root reserves of the stand.
“We see a seven to 10 percent lignin reduction, with greater harvest flexibility and more time for harvest,” Miles explains. “We also see five to 10 percent less undigested fiber and five to 10 percent digestion in our livestock, which means increased feed intake.”
Miles presented during the 2018 Forage Field Day, held in June 2018 at the James C. Hageman Sustainable Agriculture Research and Extension Center.
Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at firstname.lastname@example.org.