Wide Swathing and Low-Lignin Alfalfa – Dr. Dan Undersander, University of Wisconsin-Extension
Click here to download Undersander’s PowerPoint presentation.
In the last 80 years, milk production and the dairy industry have experienced considerable advancements. To keep up with this progress, Dr. Dan Undersander, University of Wisconsin-Extension, said we will need to continue to innovate and use technology to provide the highest quality alfalfa possible.
“We have the genetics, but we need to feed higher quality forages,” Undersander said.
Undersander told Vita Plus Custom Harvester Meeting attendees the recipe to produce a higher quality alfalfa crop is cutting when quality is highest, and reducing respiratory losses and leaf losses.
Cutting at highest quality
Undersander recommended cutting at “28 inches or 28 days, whichever comes first.”
He said every day after these two benchmarks, the yield of the crop may increase, but the quality decreases. As a percent of dry matter (DM), neutral detergent fiber (NDF) increases 0.43 percentage points and digestibility decreases 0.43 percentage points, which decreases relative forage quality (RFQ) 3.6 points each day.
Reduce respiratory losses
Plant respiration breaks down nonfiberous carbohydrate (NFC), or starches and sugars, which are 98-percent digestible and improve RFQ. Undersander said respiration continues after cutting until the plant dries below 60 percent water. When we place forage in a narrow windrow, it prevents the crop from drying rapidly, resulting in more DM losses and less available NFC.
“Every percent NFC we lose, we lose digestibility and quality,” Undersander said.
He suggested wide swathing can be used to dry the crop faster and preserve forage quality. He said wide swathing produces higher forage quality and an increased yield due to faster drying and earlier cutting to preserve NFC and offset the increased fiber. It can also increase yields on subsequent cuttings due to less wheel traffic and better irrigation.
Reduce leaf losses
The more leaves you can preserve, the higher the RFQ because the leaves are only 15 to 20 percent NDF. Undersander said the crop in the field should be 50 percent leaves. However, he said the problem is moving the crop after cutting because, every time you move it, you lose leaves.
Throughout the harvest process, he said you can see yield reductions between 5 and 20 percent from improper leaf management. Although environmental influences can impact this, he said proper management can reduce leaf losses.
Undersander transitioned to another tool that could help improve alfalfa harvest quality: low-lignin alfalfa.
Lignin is the plant cell wall component that gives plants strength to stand and transport water, but it reduces digestibility. Undersander said it is good for the plant to stand, but we don’t want more than we need. He said two products are currently available. One is a transgenic seed with a 15-percent lignin reduction and the other is a conventionally bred seed with little difference from regular alfalfa.
Unlike traditional varieties, low-lignin varieties don’t decrease in quality as quickly. Undersander explained this means it can improve forage quality, provide a wider harvest window or allow a later harvest.
According to Undersander, he said the true advantage is the later harvest. Instead of harvesting at 28 days, he said you can harvest at 32 days or later and get the same quality with a higher yield.
Additionally, he said it allows for full use of the growing season. In Madison, Wisconsin, a normal harvest schedule can run from May 20 to August 20, but, with low-lignin alfalfa, you could grow until September 5. Letting alfalfa grow the additional six days can result in an additional 2.4 tons per acre.
“I recommend taking the first cutting at the regular time because it will lodge like other alfalfa varieties and then delay each harvest after to get higher tonnage,” Undersander said.
His final reminder was to always cut above the regrowth to avoid stunting subsequent harvests.
Feed quality and nutrition