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April 26, 2007

'Don't judge a book by its cover' holds true for alfalfa crop

WEST LAFAYETTE, Ind. -
Freeze-damaged alfalfa
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Just as you can't judge a book by its cover, forage producers shouldn't judge their alfalfa crop by what they see on the outside, said a Purdue University expert.

"There is actually living green tissue and that's good," said Keith Johnson, Purdue Extension forage specialist. "Essentially, the crop is trying to start over."

Unlike some, Johnson does not recommend clipping a crop that has sustained freeze damage.

"Let the growth that is still there continue to help in the healing process of keeping photosynthesis going forward rather than clipping it all off and starting over," he said. 

Alfalfa decomposes very easily. As it rains and the plant decays, it will fall to the soil and be recycled as organic fertilizer, Johnson said. Little will end up in the baler or be fed to the animals.

"Growers need to get on their hands and knees to look at the amount of green tissue within the canopy of the crop," Johnson said. "They need to look at the development of the buds at the crown level."

While not ideal, it is encouraging to see that buds are being released in the leaf axils 2-4 inches above the ground, which also will produce for the first harvest, he said.

Johnson urged producers to dig up a few plants and split the taproots and crowns in half to look at the integrity of the roots and crowns.

Healthy tissue of the taproot, when cut into, will be firm and look like bleached wood. Decaying tissue will look light brown and will have lost its firmness. Root rot, common in older stands, may be present and should not be mistaken for freeze damage, Johnson said.

While growers are out examining taproots and crowns for healthy tissue, they also should be watching for alfalfa weevil.

"With the tissue damage that we have had, there is less of a 'meal' for them to feed upon," Johnson said. "So if the insect, the alfalfa weevil, did not decrease in population, there are many mouths of weevil to feed and less food to eat."

Weevils may not be the only ones left wanting more. Growers might not get as many cuttings as they'd like.

Due to the recent temperatures and abnormal weather patterns, the expected record early harvest is now set back, Johnson said. It is possible growers may be looking at a three-cut season, he said. This means that there will be less opportunity for a higher yield per acre at season's end.

Writer: Julie Douglas, (765) 496-1050, douglajk@purdue.edu

Source: Keith Johnson, (765) 494-4800, johnsonk@purdue.edu

Ag Communications: (765) 494-2722;
Beth Forbes, forbes@purdue.edu
Agriculture News Page

PHOTO CAPTION:
Split root and crown of freeze-damaged alfalfa shows signs of healthy tissue and new growth potential. Circled are new growth buds. (Purdue Plant and Pest Diagnostic Laboratory photo/Gail Ruhl)

A publication-quality photo is available at http://news.uns.purdue.edu/images/+2007/johnson-alfalfa.jpg

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