If alfalfa gets hit by a late-spring freeze, Peter Jeranyama's likely to recommend different cutting strategies, depending on a producer's specific needs.

“One strategy is best for maximizing forage quality over quantity and vice versa,” says Jeranyama, South Dakota State University (SDSU) extension forage crops specialist.

To maximize forage quality, he recommends clipping the alfalfa immediately after the freeze if more than one-third of the top growth is wilted or drying up. Then it should be cut for hay or silage at bud stage. To maximize yield, the field should not be clipped, and harvesting should be delayed two weeks.

“If I were a dairy producer, I would follow the first strategy,” says Jeranyama. “If I were operating a cow-calf operation, I would opt for the second one.”

He bases his recommendations on research he conducted at three locations in eastern South Dakota last year. SDSU's Vance Owens assisted with the study, on four-year-old alfalfa stands after a severe mid-May freeze. Only first cuttings were analyzed.

“Our objective was to evaluate alfalfa's reaction to a clipping after a frost,” says Jeranyama. “We also wanted to learn the impact of harvest timing following a heavy frost and to assess the impact of those treatments on forage quality.

“After a late-spring frost, I get a lot of calls from alfalfa growers asking me what they should do. Conventional wisdom says to clip the alfalfa immediately if more than one-third of the top growth is damaged. But I couldn't find any research to back that up.”

The researchers used four regimes at each location:

  • Clipped after the frost and harvested at bud stage.

  • Unclipped after the frost and harvested at bud stage.

  • Clipped with harvesting delayed two weeks.

  • Unclipped with harvesting delayed two weeks.

The highest yield — 2 tons/acre — came from the fourth treatment. The lowest yield came from the first treatment — 1 ton/acre. Treatments two and three yielded 1.7 and 1.6 tons/acre, respectively.

Relative feed value of the first treatment was 175. The others all scored around 145.