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Published May 17, 2010, 02:48 PM

Plant height should dictate alfalfa harvest

Despite recent cool weather, some of the region’s alfalfa fields are nearly ready for their first cutting of the season.

By: Jonathan Knutson, Agweek

Despite recent cool weather, some of the region’s alfalfa fields are nearly ready for their first cutting of the season.

Farmers should keep in mind that plant height is the best measure of when to harvest dairy-quality alfalfa, says J.W. Schroeder, North Dakota State University Extension Service dairy specialist.

“It’s taken some getting used to,” he says of using height instead of plant maturity, the traditional gauge of when alfalfa should be harvested.

As an alfalfa plant’s height increases, its relative feed value and forage quality decline.

According to NDSU research, 28 inches is the best height at which to harvest a field of pure alfalfa.

The University of Minnesota Extension Service also advises using plant height to decide when to cut alfalfa.

Minnesota extension officials fine-tune their recommendation on when to harvest based on the percentage of alfalfa to grass.

For instance, a 70 to 30 percent alfalfa to grass mixture should be harvested at 29 inches.

The warm spring — this was the second-warmest April in Minnesota in more than a century — means some alfalfa fields will be harvested far earlier then usual.

Producers shouldn’t necessarily harvest alfalfa early, even if they can, says Paul Peterson, forage agronomist with Minnesota extension.

Producers should wait if the alfalfa is for animals with low to medium nutritional needs or if the stand was damaged over the winter, he says.

Widespread frost across the northern Great Plains on the weekend of May 8 and 9 didn’t appear to damage alfalfa, Schroeder says.

Alfalfa typically is safe until the mercury sinks to 23 degrees, and temperatures didn’t get that low most places, he says.

It once appeared that some alfalfa in the Red River Valley of eastern North Dakota and western Minnesota could be swathed by the end of May, he says.

But recent cool weather has slowed alfalfa’s maturation and likely will push back the first cutting of many stands, he says.

Alfalfa harvesting information

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