Evaluate early June hail damage to soybeans

By Seth Naeve, Jeff Coulter and David Nicolai, University of Minnesota Extension

ST. PAUL, Minn. (6/10/2008)— Recent severe weather events across the Midwest have left crops in many parts of Minnesota affected by hail damage.

Assessing hail damage to soybeans in early June can be a bit tricky, with many variables to consider on your way to making a final decision to replant or maintain the existing stand.

One helpful resource from the University of Minnesota is the “Soybean Growers Field Guide to Evaluating Crop Damage and Replant Options,” available online at www.soybeans.umn.edu/pdfs/SoybeanCropDamage.pdf.

Here are a few key steps from that publication:

1. First, estimate the surviving plant stand. Hail damage is highly variable within fields, therefore accurate plant stands must be measured in as many locations within a management unit as possible. Making a replant decision based on a few stand counts near the field entrance will likely lead to a poor ultimate decision.

   Count several areas that are equal to 1/1000 of an acre. This is equal to a row length of 17 feet, 5 inches in 30-inch rows, and 23 feet, 9 inches in 22-inch rows. Soybean plants with significant amounts of green tissue remaining (more than one green cotyledon and/or remaining leaf tissue) are likely to survive early season hail damage.

   Soybeans can tolerate low populations very well, with only small reductions in yield potential across wide ranges in plant loss.  For instance, populations near 100,000 per acre are likely to produce maximum yields, and those around 80,000 will yield about 90 percent of the maximum.  However, expected yields drop more rapidly in stands below 50,000, with 39,000 plants per acre likely to produce about 75 percent of the normal yield.

2. Next establish the expected replant date. With widespread rain in the forecast, many fields will not be in condition to plant until after mid-June. Yield potential for late-planted soybeans drops rapidly throughout June. When compared to the yield from an early May planting, yield potentials for June 9, 14, 19, and 24 plantings are expected to be 76, 70, 64, and 57 percent, respectively.
   
   
3. Determine replant costs.  These will include time, fuel and seed costs. Additional costs may include penalties associated with variety selection when the very best genetics are no longer available. Mid-June replants should utilize soybean varieties that are approximately 0.5 maturity units shorter than full-season varieties adapted to your region. Planting in late June will require a shift of one full maturity unit.

In summary, only those fields with remaining stands below 30,000 to 40,000 plants per acre are likely to produce greater yields when replanted.

Due to increased fuel and seed costs, the economics of replanting will often be cost prohibitive with remaining stands above 30,000. So, take many stand counts throughout the field and carefully weigh the economics of the situation.

Be sure to speak with your insurer and leave appropriate check strips if needed.

Any use of this article must include the byline or following credit line:
Jeff Coulter is a corn specialist with University of Minnesota Extension, Seth Naeve is a soybean specialist with University of Minnesota Extension, and David Nicolai is an Extension educator in crops management.

Media Contact: Julie Christensen, U of M Extension, (612) 626-4077

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URL: http:// www.extension.umn.edu/extensionnews/2008/haildamageinsoybeans.html  This page was updated June 11, 2008 .
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