Grasslands Council: Learn the traffic tolerance of alfalfa

WOOSTER, Ohio – The take-home lesson from Dan Undersander’s presentation at the Ohio Forage and Grasslands Council’s 2004 annual meeting was that producers should not take the scenic route across their alfalfa fields during harvest.

Instead, they need to follow one path along the field to limit damage to the plants and a potential reduction in yield later on.

Undersander is the extension forage specialist at the University of Wisconsin.

Hardy. “It is important to recognize that alfalfa is an amazing crop,” he said. “It is amazing how hardy alfalfa is; when you talk about damage, it can still come back.”

Undersander noted that it is important to identify how much damage has happened to the stand.

Damage. Damage can happen when producers drive over the field when it is too wet, or it can happen during harvest over the summer.

“When you drive over the field, you know that you are going to do some damage,” he said.

“Research has shown that it is easy for up 50 percent of a field to have some damage due to wheel traffic.

“As much as one-fourth of the field can be damaged just in mowing and raking, and when you add harvesting such as chopping or baling, it is easy to have damage to up to 50 percent of the field.”

Varieties. Undersander added that there is a genetic difference among varieties on the impact that wheel traffic has on the stand.

“As we run variety trials, we are looking at wheel traffic,” he said.

“Some varieties are more tolerant than other varieties, but we saw that on an average, there is a 30 percent reduction in yield due to wheel traffic.”

Yield impact. He said that the number of times that a field was gone over during the harvest season also had an impact on the yield.

“We have seen as much as a 7 percent yield reduction per day due to wheel traffic,” he said.

“So you might want to drive over the field as soon as possible after cutting and manage the crop so that it dries faster. Preservatives are also an option, if you can get the hay off earlier, you are going to have a greater yield on every cutting.”

Reducing traffic. While damage from wheel traffic can’t be eliminated completely, it is possible to reduce it, according to Undersander.

“Use a smaller tractor when possible,” he said.

“It appears that if you look at average yield reduction, compaction damage to the crown plays a key role.

“Soil compaction is also a problem. Avoid unnecessary trips across the field when possible.”

Cutting ‘corners.’ Minimizing the service area will also help minimize yield reduction, according to Undersander.

“If possible, mow and condition in a single operation,” he said.

“If you have a full wagon, it needs to be hauled the length of the field rather than diagonally across the field.

“If you are dropping the bales on and collecting them later, can this be done with less driving?

“Don’t drive on the alfalfa field when you are harvesting a crop in an adjacent field.”

He added that silage production has less of an impact on the crop than hay making.

Other possibilities. Another option, is using larger equipment, as there is some indication that the less times producers drive across the field, the less yield reduction occurs.

Another option to consider is custom or contractual harvesting.

“Is the weather or soil type a determining factor,” Undersander asked. “Damage to the crop may be something that can be reduced through good management.

“If you need to apply manure to the field, you need to get it done as soon as possible.”