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Assess Alfalfa and Small Grain Winterkill Now

By   /  May 12, 2014  /  Comments Off on Assess Alfalfa and Small Grain Winterkill Now

If your winter was a hard one, no matter where you were on the planet, you’ll find this information important for making sure your plants are healthy.

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FieldPlantedWithAlfalfaThe winter of 2013-14 was long and cold and uncomfortable for most human beings in the North Country and across the Northern US.  Now that the snow has receded and soils have warmed enough to wake up most plants, it is apparent that many alfalfa and small grain fields did not endure the winter well either.  Some fields appear to have suffered extensive stand losses and will undoubtedly require reseeding or replacement.  Losses are variable and appear to be most devastating on the flatter, more poorly drained sections of fields where snowmelt and rain ponded and froze for an extended length of time.  It is important to evaluate stands early this spring to explore your options for managing winter injury and losses.

A tour across the North Country indicates that large portions of many alfalfa and small grain fields appear to be slow to ‘green up.’  These fields should be scouted for injury, frost heaving, root damage and death.  The first step in evaluating your own fields is to count the stand density or plant population, which is indicative of the yield potential of the field.  With a clipboard or notebook, walk the field in a random or ‘W’ pattern and choose 10 representative locations in the field to count the number of plants per square foot.  You can make a 12” x 12” wooden or PVC square to make this task easier.  For alfalfa, toss the square down and count and record the number of alfalfa crowns within the square.  Be sure you count crowns, not stems.  For cereals, put the square down and count the number of plants within the square.  Be sure to count cereal plants, not tillers.  Before moving on to the next location, also record whether the surviving plants appear healthy.  Dig up a couple of alfalfa plants and examine the taproot.  Is the root white, firm and healthy?  Or is it dry, brown and ‘ropey?’  If the alfalfa root is browned, dehydrated, and ropey, it is dead or dying. Do the wheat or rye plants appear to be viable?

Frost heaving exposes the roots of alfalfa plants. The exposed roots will be damaged and reduce yields within the next year or so. Image from the Ohio State University Crop Observation and Recommendation Network

Frost heaving exposes the roots of alfalfa plants. The exposed roots will be damaged and reduce yields within the next year or so. Image from the Ohio State University Crop Observation and Recommendation Network

AlfalfPopulationGuidelinesAverage the stand counts from the 10 locations within the field.  Compare the average stand count with some guidelines to understand the yield potential of the field.  For alfalfa, compare your stand counts to Table 1.  If your stand count is marginal, also consider the relative health of the surviving plants.

If alfalfa or small grain stands are below minimums, some alternative crops must be considered.  First, calculate your existing forage and grain inventories to know how much flexibility you have for reseeding and replacement crops.  If inventories are in surplus, you have the luxury of reseeding slower or later maturing crops.  However, if inventories are scarce, you’ll need to consider earlier maturing crops for quicker production.

Often, alfalfa losses will be patchy.  If you decide to continue to manage and harvest the injured field, allow alfalfa plants to mature a bit longer before cutting. This delay can help plants recover and preserve future yield potential.  For severely-damaged, but not killed, alfalfa fields, allowing plants to mature to full bloom before taking a first cut can also avoid further losses.  Delay to early flowering stage for subsequent cuttings. Increasing the cutting height may also help stands recover.  Do not harvest winter-injured stands late in the fall to allow them to store reserves before winter.  If the field is an alfalfa-grass mix, you could choose to fertilize and harvest it as a grass field.  If the losses are 25-50%, consider no-till drilling in clover or orchardgrass.  When overseeding winter-injured stands, remember to adequately fertilize and control for weeds.

Depending on degree of damage and feed inventories, consider replacing the alfalfa stand with corn, BMR sorghum, millet or another summer annual forage.  Alfalfa should not be reseeded or overseeded into the stand due to autotoxicity issues.  To quickly generate forage while also seeding a new alfalfa stand, plant another field with an alfalfa-grass mixture with an oat companion crop.  Cut the oats high at the flag leaf stage for a late July/early August forage crop.

For decision-making on an injured wheat or other small grain field, fewer than 12-15 plants per square foot is considered a minimum plant density for adequate yield potential.  Good spring populations are from 23 to 30 plants per square foot and densities above 30 plants per square foot are considered excellent.  If you’ve counted minimal plant density and the plants also do not appear healthy, consider the stand below the minimum and consider reseeding with a spring cereal or another crop.

Refer to the 2014 Cornell Guide for Integrated Field Crop Management for recommendations and guidance for planting and managing corn, soybeans, forages and small grains.

Additional resources:

  1. Evaluating Winter Injury to Alfalfa.  Jerry Cherney, Leon Hatch and Ed Goyette, Cornell University.  http://forages.org/page.php?pid=44.
  2. Alfalfa stand assessment:  Is this stand good enough to keep?  2011. Undersander et al, Univ Wisconsin Extension.  http://learningstore.uwex.edu/assets/pdfs/a3620.pdf
  3. Assessing Alfalfa Stand Conditions in the Spring.  2013. Undersander et al, Univ Wisconsin Extension.  http://fyi.uwex.edu/drought2012/files/2013/04/Assessing-Alfalfa-Stand-Condition-in-the-Spring.pdf
  4. Wheat Stand Assessment, Winterkill Yield loss, and Nitrogen Application.  Conley & Gaska.  Univ Wisconsin Extension.   http://www.coolbean.info/pdf/small_grains/early_season/Wheat_Winterkill_09.pdf
  5. 2014 Cornell Guide for Integrated Field Crop Management.  2014.  Bill Cox, ed.  Cornell Univ. Cooperative Extension.

PssstSupportOnPasturesmFor more information about field crop and soil management, contact your local Cornell Cooperative Extension office or Kitty O’Neil, CCE of Northern NY, 315-379- 9192 x253; kao32@cornell.edu, or head to your local NRCS, extension, or conservation district office for suggestions.

 

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