Potential Effect of Weekend Freezes on Corn and Soybean

Chad Lee, Conner Raymond, and Carrie Knott; University of Kentucky

Freezing temperatures were recorded across Kentucky Monday morning, April 24, 2023. The coldest temperatures were mostly in central and eastern Kentucky, but freezing temperatures were as far west as Trigg and Webster counties. Temperatures fell to or slightly below freezing in the following counties from Sunday to Monday: Butler, Caldwell, Carroll, Christian, Crittenden, Graves, Grayson, Hardin, Logan, Meade, Ohio, Taylor, and Webster counties (Table 1, at the end of this article). Webster and McLean County were the coldest at 30°F. Frosts likely occurred west of these counties. The good news is that soil surface temperatures likely stayed in the low 50’s to mid-40’s. This is based on soil surface temperatures measured at UKREC in Princeton, KY.

About 36% of corn acres and 20% of soybean acres were planted as of April 23, 2023, according to the USDA-NASS.

Corn and Soybeans at Risk

Corn and soybeans are at more risk to death from the freeze events at specific growth stages and in certain conditions. The following scenarios go from greatest risk to least risk of plant death from the freeze events.

Soybeans at the “crook” stage where the stem is emerged and bent over like a shepherd’s crook were the most susceptible to the freeze (Figure 1). These plants were most likely to be killed by the freeze or frost. At crook stage, typical damage is along the stem with some yellowing of the cotyledon. This will be followed by plants snapping off where damage was observed (Figures 2 and 3).

Corn and soybean seeds and seedlings in furrows that were not fully closed are at risk of being killed by the freeze.

Corn or soybean seeds that were planted shallow had a slight risk of freeze damage, although plant death from the freeze is unlikely.

Corn plants emerged may have tissue above the soil surface die off from the freeze, but the growing points should have been insulated beneath the soil surface.  Those corn plants should recover well. No yield loss is expected.

Soybean plants that have FULLY emerged and are at the VE growth stage (emergence) should survive the freeze event, based on observations during freeze events in late April 2021 and early May 2020. If the soybean cotyledons survive, the soybean plants will survive, and no yield loss will occur. If the cotyledons do not survive, the plant will not survive, either. 

Corn and soybean seeds at proper planting depths are at very little risk from the freeze. Corn and soybean radicles (the shoots emerging from the seeds) that are still below the soil surface likely were insulated and will survive.

We need about 5 days of warm weather before symptoms are easy to see. Based on current forecasts, it may take six or seven actual days to get the 5 days of good growing conditions. Plants or plant parts that have turned black or brown and have lost turgor pressure are easy to identify.

Corn plants need to be examined from the seed upward. We are assuming that the roots are deep enough to not be a concern. Dig up some corn plants and look for any signs of brown/black areas from the seeds upward. If plants are white to yellow beneath the soil and turgor pressure is good, then the seedlings are likely to survive.  

Maybe Just a Chill

Corn and soybean seeds that are in the process of germinating during the freeze are at risk of taking in cold water (imbibitional chilling) within the first 24 to 48 hours after planting. If the soil temperatures were below 50F for an extended period during those 24 to 48 hours, then the seeds are more likely to be damaged. There is some debate about how long the soils need to stay below 50F before severe damage is done from the imbibitional chilling. We can say those seeds are at risk. At this point, either the seeds were damaged, or they were not from imbibitional chilling. Emergence will be slower in these fields. The fields can be scouted in about five days or so to determine the health of germinating seeds and/or emerged plants.

Table 1: Low temperatures recorded across the state from 4/21/23 through 4/24/23. Freezing temperatures are highlighted in light blue. Weather data from the Kentucky Mesonet.

 Low Temperature °F3 Day
KY Mesonet Site4/21-224/22-234/23-24Average Low
    Temperature
Adair48413441
Allen49413541
Ballard42383538
Barren49403441
Bath54433745
Boone46373439
Boyle47423341
Breathitt58463847
Breckinridge46393339
Bullitt47393440
Butler45383238
Caldwell42353236
Calloway42393538
Campbell47403540
Carroll47363238
Casey48423341
Christian43383338
Clark48423642
Clinton48413441
Crittenden43353237
Cumberland49413441
Fayette48413541
Franklin47383540
Fulton42393639
Graves42363337
Grayson45393238
Hardin47393239
Harrison48373340
Hart47393540
Henderson47383640
Hopkins45373438
LaRue47413441
Lewis46453642
Lincoln47413441
Logan46363238
Madison51443643
Marion47413340
Marshall43363337
Mason52393642
McLean48383440
Meade47353037
Mercer48413441
Metcalfe47403541
Monroe49423743
Morgan56473546
Muhlenberg45363238
Nicholas49413642
Ohio45383138
Oldham46383540
Owen45373539
Owsley50443443
Pike55423544
Pulaski49423442
Rowan52433845
Shelby47353539
Simpson48393741
Taylor48423240
Todd43373438
Trigg43383438
Union45373438
Warren48393641
Wayne49443643
Webster43353036


Resources

Coulter, Jeff. 2021. Spring Freeze Injury in Corn. University of Minnesota Extension. https://extension.umn.edu/growing-corn/spring-freeze-injury-corn

KY Climate Center. 2023. Kentucky Mesonet. https://www.kymesonet.org/ accessed April 24, 2023.

Lee, C.D. Evaluating early season frost damage to corn. AGR-192. Univ. of Kentucky Cooperative Extension Service. http://www2.ca.uky.edu/agcomm/pubs/agr/agr192/agr192.pdf

Nielsen, R.L. 2020. Assessing Frost/Cold Temperature Injury to Young Corn. Corny News Network. http://www.kingcorn.org/news/timeless/FrostedCorn.html

Nielsen, R.L. 2020. Cold Soils & Risk of Imbibitional Chilling Injury in Corn. Corny News Network. Purdue Univ. https://www.agry.purdue.edu/ext/corn/news/timeless/ImbibitionalChilling.html

Staton, Michael. 2021. Assessing frost/freeze damage to emerged soybeans. Michigan State University Extension. https://www.canr.msu.edu/news/assessing-low-temperature-injury-to-soybeans

Taylor, M., A. Nygren, J. Rees., J. Specht and A. Timmerman. 2020. Evaluating freeze and chilling injury in corn and soybeans. Nebraska Cropwatch. https://cropwatch.unl.edu/2020/evaluating-freeze-and-chilling-injury-corn-and-soybeans

USDA-NASS. 2023. USDA-NASS. Crop Progress and Condition. https://www.nass.usda.gov/Statistics_by_State/Kentucky/Publications/Crop_Progress_&_Condition/cw23/CW042423.pdf

Posted on April 28, 2023, in Uncategorized and tagged , , . Bookmark the permalink. Leave a comment.

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