Alfalfa leaves key to quality and yield

Colleen Kottke
Wisconsin State Farmer

MADISON - If there are more leaves left laying in the hayfield, it's time to take a look your harvesting process.

University of Wisconsin Madison Agronomy Professor Dan Undersander told farmers attending the Vita Plus Dairy Summit held recently in Madison, that the bulk of nutrition of an alfalfa plant is in the leaves. Disease, rain, and harvesting equipment can strip the nutrition-packed leaves from the stem and leave cows wanting more.

Dan Undersander

Undersander said that honing forage management processes can go a long ways in making sure producers are harvesting hay at its optimum nutritional value in a timely and efficient manner.

Standing alfalfa plants contain 50 percent leaves and 50 percent stems before mowing. That ratio can drop anywhere from one-third leaves to two-thirds stems.

"The difference in forage quality is due to leaf content. Think of yourself as harvesting leaves, not just in tonnage," Undersander said. "Stems give us a little bit of fiber but we really need to focus on the leaves."

Undersander said producers can maintain leaves throughout the harvesting process if they're careful on how they manage that forage.

A rotary rake helps to merge swaths into a windrow.

"Meaning how little we shake it along the way," he said. "Five to seven percent leaf loss is about as good as we can do. But remember, that's a loss in yield."

Shutting down respiration

The respiration process, which breaks down sugars and starches in the plants, continues even after alfalfa plants are cut, he said. 

"When you cut alfalfa it's about 75-80 percent water and until it dries down to about 60 percent the respiration continues at a near to normal rate," Undersander said. "Cutting the hay and putting it into a wide swath and shutting down respiration as soon as possible is one of the key things in maintaining the quality in the forage."

Leaf loss

Undersander told farmers to inspect alfalfa fields before cutting, looking for leaf loss. Leaves laying on the ground could indicate the presence of disease.

"The presence of disease depends on weather conditions. If it's wet we tend to have a lot of disease, in dry conditions not so much," he said.

Leaves laying on the ground after mowing means farmers need to uncover the root of the problem for leaf loss, including the machinery that may need adjustment. Undersander says he prefers a roller conditioner over a flail conditioner for harvesting alfalfa and recommends tedding only on grasses.

"Just look at how much you're shaking the leaves," Undersander said.

Moisture matters

The agronomy professor also recommends raking hay at 50 percent moisture to avoid leaf shattering.

"You want to rake hay before it really gets too dry and the leaves are turning brown — that's when a lot of the leaf loss is occurring," he said. "Harvesting with dew on the windrow also helps add moisture and reduce leaf loss."

Poorly adjusted harvest equipment could also be adding unwanted ingredients into animal's diets. Adjusting the cutter bar height on the mower helps to reduce the amount of ash and dirt contained in newly cut hay.

Adjusting a disk cutter bar will help to reduce the amount of ash incorporated into the alfalfa.

"You can't put up hay without getting any ash and the goal is to be at 10 percent or less ash. I've seen a few samples in the lab where there was 28 percent ash content," he said. "That person was feeding one pound of dirt for every two pounds of feed. You think those cows milk really well?"

Making adjustments

Undersander said he recommends a 3-inch cutter bar height, making sure the teeth don't hit the ground. Tines from the wheels on a rake can also add dirt during the raking process.

"The machinery industry tells me that the most common repairs on rakes is bent and broken teeth, meaning we're digging too much dirt," he said.

While many farmers are trying to get the hay harvested off their fields as quickly as possible, especially if rain is in the forecast, the speed at which they're harvesting could work against them, he said.

A wheel rake merges two swaths of alfalfa into one windrow.

"I see harried farmers trying to go a little faster and they're really throwing that hay around," he said. "Ask yourself, do you have the right PTO speed and ground speed for the conditions that you're raking in? The optimum speed should be between 5-7 mph."

Wheel traffic

Just the act of driving up and down the field mowing, raking and harvesting takes a toll not only on the plants being harvested but the next crop.

"Every time you drive over alfalfa (breaking the stems) there is a cost: loss of yield," Undersander said. "According to studies that we did, reducing the amount of wheel traffic resulted in an extra half-ton to one ton of yield - and that's a big deal."

To minimize the number of wheels trampling alfalfa plants, Undersander suggests putting as many swathes as possible into a windrow, or using a wider mower.

That green cloud over the truck and harvesting machine is tiny bits of shattered alfalfa leaves.

Within five days, shoots on the alfalfa plants covered by the newly mowed hay are starting to send out shoots.

"One of the reasons that silage fields for alfalfa yield more than hay fields is that you can get it off in a day or two, and hay is going to take you three to five days," Undersander said. "Wheel traffic in the field closer to cutting time helps to minimize the damage and the yield reduction of the next crop."

He noted that fall dormant types of hay tend to come back faster after cutting.

"Sometimes it comes back so fast that you can't get the newly cut crop off the field before the shoots have regrown," he said.