There are better ways to determine when to cut first- and second-crop alfalfa for optimal quality than looking at stage of maturity or the calendar.

It's more accurate to use a PEAQ stick or calculate heat units, known as growing degree days (GDDs), says Richard Leep, Michigan State University (MSU) extension forage specialist.

“Visually analyzing the alfalfa for the best time to cut is subjective,” says Leep. “What's early bud stage to one grower isn't necessarily early bud stage to another.”

The PEAQ (Predictive Equations for Alfalfa Quality) method was developed in the 1990s by University of Wisconsin-Madison researchers. It uses plant height and maturity stage to estimate alfalfa quality. Sticks can be calibrated to measure NDF, ADF or RFV.

Alfalfa growers can begin tracking GDDs as soon as alfalfa plants break dormancy and actively start growing, says Leep. That's usually around March 1 in Michigan.

NDF increases about 0.04 point for each GDD. GDDs accumulate whenever the average daily temperature exceeds 41°, and can be as high as 40 GDDs/day.

“We recommend growers take their first cuttings when GDDs hit 750,” he advises. “That will give you 40% NDF, which is ideal for high-producing dairy cows.”

County extension agents compared four methods for timing cuttings at many sites on Michigan farms. They tracked GDDs, used PEAQ sticks and looked at the calendar or at physiological indicators like bud formation. Samples were analyzed using wet chemistry.

In the first cutting, the PEAQ and GDDs were equally effective at hitting the 40%-NDF target. In the second cutting, the PEAQ stick narrowly edged GDDs as the more accurate method. Both were better than the other two.

“Those two methods didn't work as well with subsequent cuttings because we tend to get into drier weather in July and August,” says Leep. “Once you get to later cuttings, use either hand clippings for analysis or growth stage.”

Whether to use a PEAQ stick or track GDDs is a matter of personal preference, he says. “On one hand, GDDs can be tracked from indoors, but using a PEAQ stick in the field gives you the opportunity to scout for insects and monitor plant health at the same time.”

Track GDDs using a thermometer that records the minimum and maximum daily temperatures or glean the information from a weather Web site, recommends Doo-Hong Min, an MSU extension forage specialist in the Upper Peninsula.

To calculate GDDs, average the minimum and maximum daily temperatures and subtract 41. For example, if the daily high and low temperatures are 65 and 43, the GDDs are 13 (65 + 43 = 108/2 - 41 = 13).

One final caution: GDDs should only be used with pure alfalfa, not alfalfa-grass mixtures, says Min.

Finding PEAQ Sticks

PEAQ sticks and instructions are available from many seed companies and state forage councils. They can also be ordered through the Midwest Forage Association at

GDDs Aid Late-Season Cutting Decisions

Historical weather data can help determine the probability that you can safely harvest alfalfa late in the season, say Richard Leep and Doo-Hong Min, Michigan State University extension forage specialists.

In late summer and early fall, alfalfa must be cut early enough so it can regrow and then replenish root carbohydrates and proteins, or so late that regrowth is minimal. In the past that resulted in the recommendation of a no-cut window from Sept. 1 to killing frost in Michigan, says Leep.

But recent Quebec research has redefined that window. It shows that, if 500 growing degree days (GDDs) accumulate after the last cutting in late summer, there will be enough regrowth for good carbohydrate accumulation before a killing frost. So a grower can cut in September as long as enough warm weather remains before a killing frost.

The research also showed that cutting alfalfa later in fall is acceptable if less than 200 GDDs accumulate between the cutting and the first killing frost. In that scenario, there's little regrowth to use up stored carbohydrates and proteins, resulting in good winter survival.

“But if you harvest after a killing frost, GDDs don't matter,” says Leep.

To make the Quebec recommendations more helpful, Leep and MSU climatologist Jeffrey Andreson analyzed 30 years of daily climate data from 30 Michigan sites. They calculated the probabilities of reaching 500 GDDs after a late-summer cutting or 200 GDDs after a fall cutting to estimate the risk of winter injury due to harvesting at various dates.

For example, the climate data from the central Michigan town of Alma shows an 85% probability of reaching 500 GDDs before a killing frost if alfalfa is cut Sept. 15 and a 20% probability if it's cut Sept. 29. Waiting to cut until Oct. 27 shows an 80% probability of reaching less than 200 GDDs before a killing frost.

Leep and Min got the idea to analyze the climate data from Dan Undersander, University of Wisconsin extension forage specialist, who did the same thing for several locations in that state.

Because weather varies from one state to another, Leep says growers should encourage forage specialists in their states to chart such data.

For more information, Wisconsin growers can visit Click on “Late Summer Cutting Management of Alfalfa” under the Alfalfa Harvest Management heading. In Michigan, visit sion.htm. Click on “Fall Cutting Management of Alfalfa.”

Alfalfa Processing Plant Closes

The Heartland Feed alfalfa processing plant in Tioga, ND, has ceased operations, according to media reports from Williston. The plant received over $1.5 million dollars in economic development funding; some of the money is not likely to be recovered, say state economic development officials.

Heartland Feed opened about two years ago with hopes of creating about a dozen jobs by making alfalfa pellets for sale to livestock handlers around the world.