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Helping forage stands recover


Many pastures and hay fields were damaged by the extreme drought conditions of 2012 and are still in recovery mode. What can you do now to help? In the case of hay fields, should you leave the stand for one more year or make a new seeding in another field to replace it? Iowa State University Extension forage agronomist Steve Barnhart suggests some things to think about as you prioritize your management options.

First, determine how well the forage stand survived winter. When evaluating winter injury in alfalfa fields, consider both the number of plants per square foot, the age of the stand and general root and crown health. Crown and root diseases develop as stands age and often reduce stand density. Check plants for dead, dying or diseased tissue this spring.

Wait until spring growth is about 3 to 4 inches high. Select random stand count sites that represent the variability of the field. Check at least one place in the field for every 5 to 10 acres.

At each site, dig up the plants in an area of 1 square foot. Look carefully at the crown buds to determine if the tissue is still alive. Count the number of live plants per square foot.

Use the table accompanying this article to begin the rating of your stand. Split the taproots and evaluate their general health. Refer to the illustrations of taproot damage shown in ISU Extension publication “Evaluation for winter injury” at www.extension.iastate.edu/Publications/PM1362.pdf.

Check health of taproots

The interior of healthy taproots is firm and creamy-white, says Barnhart. Damaged or dying taproots are yellowish-brown to chocolate-brown in color, and watery or dry to fibrous in texture. Only healthy plants will contribute significantly to yield. If any of the taproots are more than 50% diseased, reduce your initial stand count accordingly.

Another option is to use the stems-per-square-foot assessment method. It’s also explained in the ISU publication on evaluating winter injury. It takes about 55 or more stems per square foot to indicate that stand density is not limiting yield, he says.

Again, refer to the illustration of the roots to evaluate the general health of the taproots with the stems-per-square-foot assessment method. Whether using “plants per square foot” or “stems per square foot,” you should adjust your alfalfa stand assessment as needed.

Winter-injured alfalfa plants are slow to recover in spring, so a quick decision to destroy a winter-injured stand is not recommended. After the first check, recheck the winter-injured fields after two weeks more growth.

When evaluating stands for other forage legumes such as red clover, Barnhart says you should use the same general guidelines as for alfalfa. Pasture areas with greater than 70% live sod cover are most desirable. With less than 70% sod cover, consider frost seeding or interseeding as described in the ISU reference publications.

Winter-injured pasture plants are often slow to recover in spring, so a quick decision to destroy a winter-injured pasture stand isn’t recommended.

Management tips for 2013

Plan your forage crop management in 2013 based on your stand evaluations, he advises. If harvesting winter-injured stands this year, let plants mature to 10% to 25% bloom or later, before cutting. Increase cutting height to 3 to 4 inches. Maintain good fertilizer and insect management.

Replant or overseed (frost seeding or interseeding) thin stands, where appropriate. “Don’t overseed thin alfalfa stands with more alfalfa,” says Barnhart. “Frost-seeding red clover or interseeding red clover or orchardgrass would be better choices.”

Expect significant loss in 2013 if stands are severely winter injured. Plan to re-establish a new hayfield this spring in this case, and begin to plan for any needed supplemental harvested and stored forage needs.

“Alfalfa Management Guide” is a publication you can find at the ISU extension online store at www.extension.iastate.edu. Click on the Extension Store link “Browse the store” and look for publication number NCR 0547. Other helpful publications you can find are “Establishing new forage stands,” PM 1008.pdf; “Evaluation for winter injury,” PM 1362.pdf; “Interseeding and no-till renovation,” PM 1097.pdf; and “Selecting forage species,” PM 1792.pdf.

Source: ISU Extension

Age of alfalfa stand and rating of winter survival

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* Alfalfa plants in thin stands often produce more individual stems per plant and compensate some in yield potential

** If 50% or more of the plants have crown or root rot, consider reseeding.

This article published in the March, 2013 edition of WALLACES FARMER.

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