This Might Be Year For Fall-Harvested Alfalfa

By Jane Fyksen Crops Editor
Thursday, August 28, 2008 8:22 AM CDT

If dairy and livestock producers have never taken a late harvest of alfalfa, this may be a good year to give it a try, maintains University of Minnesota agronomist Paul Peterson.

High-quality forage supplies are short due to various weather challenges; alfalfa prices remain strong. Forage is becoming a more valuable commodity with each passing month, in light of high grain and energy costs. Late summer into fall usually provides favorable growing conditions for alfalfa growth. Peterson thinks growers should consider harvesting that growth this year.

Timing the fall cut isn’t as important as traditionally thought, according to Peterson. “Research data continue to mount supporting the concept that timing of the fall cut matters little as long as other factors - variety, fertility, drainage - favor fall-cutting tolerance,” he says.

“Farmer experience must agree, as I have noted more September cutting in my travels over the last several years,” he adds.

“However, for the risk-averse, either avoiding fall cutting or waiting until mid-October may be better options. Waiting until mid-October minimizes the chances of significant regrowth and root reserve depletion after cutting,” he notes. “But don’t be concerned about waiting for an alfalfa-herbage-killing frost - around 20 degrees - before harvesting.” That approach risks significant leaf loss and unfavorable curing conditions.

Previous cutting frequency plays into the equation, though. Stands cut more frequently are at greater risk of winter injury if cut during the fall. However, when other factors favor fall-cutting tolerance, a third harvest during the fall is rarely risky, says Peterson. A fourth harvest during fall can be somewhat risky, on the other hand. A fifth cut during fall carries considerable risk.

Key to enhancing winter survival is allowing at least one crop during the growing season to mature to mid-bloom. Thus, stands of fall forage that have previously been cut at pre-bloom stages should be well-flowered if fall harvest is considered, Peterson advises.

Recent North Dakota data sheds some new light on fall-harvested alfalfa. Working with two varieties in replicated plots at Fargo, researcher Dwain Meyer showed a three-year total yield gain of 3.6 tons per acre by taking a fourth harvest in fall for three consecutive years, compared to just three harvests per year. A key aspect of his four-cut system was that the fourth harvest was taken when alfalfa plants attained either 40 to 50 percent bloom or 2 to 3 inches of new shoot growth from the crown. That corresponded to Oct. 7, Sept. 28, and Sept. 13 in 2004, 2005 and 2006, respectively. “There was little to no evidence of winter injury each spring through 2007,” Peterson adds.

Growers will understandably be concerned about quality and yield next spring.

“We’ve conducted fall-cutting experiments on two farms in southeastern Minnesota. On one farm, fall residue after a third cutting in mid-August significantly reduced quality of the next year’s first cutting. On the second farm, it did not,” Peterson reports, adding that some Wisconsin data indicates little affect of fall residue on spring quality.

“Thus, fall residue more often than not has little detrimental affect on quality the next spring,” he states.

If, however, there’s a lot of fall residue and it doesn’t get matted down by snow over winter, it may reduce quality next spring. “If that is a concern next spring, fall residue can be clipped when the ground is still frozen before spring regrowth starts,” he advises. Peterson understands this can, however, be a challenge to time without damaging the stand.

He says fall cutting can delay growth next spring. “While this can be alarming initially, especially when neighboring non-fall-cut fields of alfalfa are jumping, any yield delay or loss is usually far less than the yield harvested n gained - the previous fall,” this forage agronomist assures.

Grazing is a great option for “harvesting” alfalfa in the fall. Grazing cattle and other livestock often leave stemmy stubble for catching insulating snow. Be careful about grazing when the soil is wet from fall rains, because stand damage will occur. Alfalfa-grass mixtures can be grazed during somewhat wetter fall conditions than pure alfalfa.

Follow bloat precautions if grazing pure alfalfa, especially right after a killing frost.

Some growers may be tempted to leave uncut strips and/or a higher residual height. Peterson notes that while there’s no research data substantiating the benefit of leaving uncut strips less than 20 feet apart perpendicular to prevailing winter winds to help catch insulating snow for winter survival, “anecdotal evidence suggests” this practice may reduce fall-harvest risk. So will leaving stubble taller than six inches to enhance snow cover.

Growers might consider shortening up their rotations as companion management to fall-harvested alfalfa. “Even the best varieties with the best management begin to lose yield potential in their third year,” states Peterson. “Thus, on many farms where nitrogen credits from alfalfa can be effectively used by a subsequent corn crop, keeping stands beyond three to four years may not be economical.”

Remember that stands need over 55 stems per square foot for greatest yield potential. Stands in the range of 30 to 40 stems per square foot “may not appear to be weak from the road,” but they still lack the yield potential of denser, healthier stands, Peterson points out.

“Alfalfa production costs are too high to limp along with marginal yields,” he tells growers. “If you lose a stand due to fall cutting, capitalize on the latest alfalfa genetics in another field next spring - and consider mixing with a high-yielding, hardy grass for insurance.”

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