When Should You Cut First Crop Alfalfa?

Harvest first crop alfalfa to maximize quality and quantity. ( Farm Journal )

Depending on where you are in the country, and what your spring weather has been like, you’re either getting ready to take first crop alfalfa off the field or it’s already chopped or baled. Regardless of your situation, that first cutting of alfalfa is important.

If weather cooperates, first cutting is usually the highest quality, and it also makes up about 40% of the overall yield in a 4-cut system. The question is, do you want to cut it early to get the highest quality or wait a bit longer to harvest more quantity?

“For dairy cows, I want to have very high-quality forage due to milk production, but there’s always a trade-off,” says Phil Kaatz, Michigan State University Extension. “To have high quality, producers will end up decreasing the yield that comes out of the field, especially in first cutting. I tell my dairy producers, ‘I would rather be a day early cutting alfalfa than a day late.’ Because if I’m a day late, the quality I have out there is going to decrease very quickly.”

The question is, then, when do I cut? Following one simple rule, according to Randy Welch, national alfalfa agronomist with Croplan Winfield United, will go a long way toward achieving the quality and quantity balance. 

“To get that first cutting harvested properly, we need to harvest based on plant height,” Welch says. “28 inches is the height you want to be cutting at. Depending on where you are, your crop might not hit that height until May 20. Or if you’re farther north, it might not be until the first of June.”

Measure the height at the top of the plant, not the tip of the leaflet, says Dan Undersander, professor emeritus at the University of Wisconsin. 

‘Harvest at 28-29 inches in height to get the best compromise between yield and quality of the crop,” Undersander says. “Research findings show a daily change of -0.25% crude protein, +0.36% acid detergent fiber and +0.43% neutral detergent fiber as the alfalfa matures.”

Basing your cutting decision off of plant height is the most accurate way to gauge when a crop is ready to harvest on your specific fields, Welch says. Heat units are another way to measure when the crop is ready, but he says that can sometimes be based on the weather far away from your farm. 

“All you need is a standard measuring device, like a simple yard stick, and you can make decisions for your farm based on each field. Is it north slope, south slope, dry ground, wet ground, irrigated or not,” he says. 

Don’t start getting equipment ready when plants hit 28 inches, Welch says. Have everything ready to go so when the plants are ready, you’re ready. 

“When plants hit about 26 inches you better have your haybine out of the shed, greased up and ready to go,” Welch says. “Alfalfa grows about an inch each day, at 50-55 stems per square foot that’s about 100 to 125 pounds of dry matter per inch of height, and that’s why timing is so important.”