How can a grower get higher alfalfa yields and quality, greater nitrogen credits and increased corn yields?

By ripping up alfalfa stands over three years in age, says Dan Undersander, University of Wisconsin extension forage agronomist.

A short alfalfa stand — the seeding year plus two more — is more profitable than keeping a stand four or more years, says Undersander. He studied the cost difference of several alfalfa stand lengths using Agriculture Budget Calculation Software. Ken Barnett, University of Wisconsin extension educator, used the same software while studying the costs of various alfalfa rotations with corn. Although they used different scenarios, they came up with the same conclusion.

“We have two changes going on now that really favor taking advantage of shorter alfalfa rotations,” explains Undersander. “The first is that the cost of nitrogen is much more than it was a few years ago. So the value of the legume credits and turning over that stand are higher.”

He compared three-year and five-year alfalfa stands on a 300-acre farm with 200 acres of alfalfa, 60 of corn grain and 40 of corn silage. He found that three years of alfalfa increased legume credits to $10.61 per acre over the five-year rotation total of $6.40. The three-year stand also provided annual corn grain ($6/acre), silage ($9.45/acre) and alfalfa ($17.83/acre) yield increases, making a profit boost of $23.46/acre/year from that stand. Expenses were $6.07/acre higher for the short rotation.

“The second change favoring short stands is that the cost of corn seed has increased more than the cost of alfalfa,” says Undersander. “Costs are equal or greater to seed an acre of corn than an acre of alfalfa.”

People used to complain about the high cost of alfalfa seed, he adds. “But with the new corn traits, the cost of corn seed has gone up dramatically. The cost of corn is $150-200/bag (covering about 2⅔ acres). So take a bag at, say, $180 and divide it by 2.67; you get $67/acre. All of the sudden, the cost of corn is more than the cost of alfalfa seed.”

When Barnett analyzed the economics of six alfalfa-corn rotations, he was attempting to see if corn silage or alfalfa was most profitable.

He found that a four-year rotation consisting of a seeding year, two years of alfalfa and one of corn brought in the most money, at $92/acre for the duration of the rotation. A three-year rotation of alfalfa establishment, alfalfa and corn was least profitable ($51), followed by a five-year rotation that included the seeding year, two years of alfalfa and two years of corn ($59).

For more on Barnett's research, visit cdp.wisc.edu/pdf/rotationalfalfa%20and%20corn%20silage%202004.pdf.

The biggest reason for replacing alfalfa stands after two full production years is the fact that yields drop off dramatically as the crop ages, says Undersander.

Studies have shown that alfalfa yields decline by 10% in the third production year and 24% in the fourth production year. By plowing stands down before production wanes and replacing them with new plants, yields increase, as does forage quality, he adds.

Corn following alfalfa yields 10% more than corn following corn, so corn yields also increase. Another benefit to short stands is being able to take advantage of the improved genetics in new varieties.

The downside of ripping out alfalfa sooner, besides the labor involved, has always been establishment-year costs. But Undersander emphasizes that the higher yield benefits — and the extra N credits — outweigh those costs.

Another downside has been that alfalfa yields only about 40% as much forage in the seeding year as in the first full production year. For ways to increase yields during the establishment year, see the accompanying story.

Enhancing Seeding-Year Yields

If you're considering replacing your alfalfa stands sooner — or even if you're not — there are three things you can do to add yield in the establishment year. So says Dan Undersander, University of Wisconsin extension forage agronomist.

One is to carefully pick varieties that yield well in the seeding year, he says.

“Our studies have shown every year that some varieties yield about ½ ton more in the seeding year than others.”

You may also want to consider seeding Italian ryegrass along with the alfalfa, he suggests.

“It is high-yielding in the seeding year and is almost the same in quality as alfalfa. There are a lot of other crops we could put on top of alfalfa, like oats, but it's not as palatable or as high in energy and protein.” (For more on Italian ryegrass, see our January issue, page 28.)

Another option for growers who want a grass-legume mix is perennial ryegrass. “The perennial ryegrass may not have as much yield as some of the Italians, but it will yield more consistently throughout the season. If you get good snow cover, it may survive into the next year or two down the road.”

The third way to increase establishment-year profits is to take the first cutting early — no more than 60 days after seeding, he adds.

“A lot of people would let it go to flower and figure they ought to go easy on it. But, in fact, they should be cutting it early because then they would be getting more tonnage.

“Then, of course, we should also mention that soil pH should be at 6.8 and that a good supply of potassium, sulfur and boron is needed for good fertility management,” Undersander says.