Cut, rake, bale; cut, rake, bale; cut, rake, bale. Result: lost yield.

Whatever your alfalfa harvest cadence, you get the picture. Research shows it's time to take aim at reducing the stress of 10,000 lbs of heavy metal and rubber on alfalfa plants trip after trip. Why? Yield losses as high as 70% in research plots.

“I was shocked at the amount of yield loss due to wheel damage that we've seen in our first two years of study,” says Dan Undersander, University of Wisconsin extension forage agronomist. “That's why a cooperative research effort is under way across six states to collect more data on plant damage and soil compaction caused by specific traffic patterns.”

In the two years of trials, Undersander found some big genetic differences among varieties in how they handle traffic. One commonsense belief is that varieties with strong grazing tolerance will be best at handling the stress of wheel traffic.

“We're not just researching grazing-type varieties,” Undersander says. “I would say as a general rule that maybe the grazing types will do better in this type of test than others, but that's not necessarily the case.

“For instance, Geneva (not a grazing-type variety) did almost as well as some of the grazing types in our trials,” he says.

Will “traffic tolerance” climb to the top of the varietal selection criteria ladder, ranking up there with yield potential and pest resistance?

Jim Moutray, director of research with America's Alfalfa, believes traffic tolerance should be a standard selection trait, “kind of like standard equipment, so to speak,” he says. “Traffic occurs on every alfalfa field, and yield loss from wheel damage occurs with every variety, so this is valuable information for every alfalfa producer.”

Moutray's company discovered the potential of a traffic trait several years ago while working on grazing tolerance. Now it's marketing several varieties as “traffic tested,” and other companies are beginning to follow suit.

Undersander's best advice is to ask companies for research to justify the claims.

“We really don't have enough data at this point about which plant traits help a variety better survive traffic,” he says.

“I think maybe there are certain characteristics, such as crown height, that seem logical. Frankly, we haven't identified the traits that are important yet. But this year's six-state project will help us gain this information.”

Until more research provides better varietal answers, Undersander lists a few things a farmer can do to better-manage traffic in alfalfa fields:

  1. Avoid unnecessary trips across the field when harvesting.

  2. Consider using larger equipment. This could be another benefit of contract harvesting. However, there's some question about it because, while the wheels of big equipment affect less area, they carry more weight.

  3. Do necessary driving on fields as soon after cutting as possible.