Lebanon Crop Management Video

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05 April 2016

Risk of Freeze Damage to Winter Grains

Del Voight - Penn State Extension

As winter grains are in a susceptible growth stage and the second  impending freeze forecasted for tonight. It might be a good idea to print off this fact sheet and review what to expect.  In as little as 2 hours of a freeze below 30 the result could  impact the crop yield of this 2016 crop as it has progressed beyond normal growth from early seeding last fall. As it begins to form the head at jointing  stage it must be protected from weather, pests and nutrient deficiencies. Here is a  photo I took about a week after a 19 degree overnight temperature of some tip burn from some wheat in the jointing stage. This has little impact on yield.   It takes time to really assess these fields perhaps 10 days to really know and assess damage. Time will tell how deep the freeze occurred and the impact on the head.

Here is a picture of what the plant is doing right now at jointing with the hollow stem and the small seed head forming above that point.  (Source Arkansas University Extension)  I was involved in some cases where liquid nitrogen applications  burned the wheat below the head and this resulted in a complete loss in the fields that were burned by the liquid N. This would be similar to this situation if the freeze reaches and destroys the tender seed head inside.
Dr Chad Lee in Kentucky has a nice factsheet detailing wheat and freeze damage.  The table below is an excerpt from his writings and it provides the temperature and hours to become an issue.  Freeze damage affect on Wheat.(Kentucky Extension)
Table 3-3. Freeze injury in wheat.*
Growth stageFeekesZadoksApproximate injurious temp. (2 hrs)
Primary symptoms
Yield effect
Tillering**1-520-2912°FLeaf chlorosis; burning of leaf tips; silage odor; blue cast to fieldsSlight to moderate
Jointing(6-7)31-3224°FDeath of growing point; leaf yellowing or burning; lesions, splitting, or bending of lower stem; odorModerate to severe
Boot1041-4928°FFloret sterility; spike trapped in boot; damage to lower stem; leaf discoloration; odorModerate to severe
Heading10.1-.550-5830°FFloret sterility; white awns or white spikes; damage to lower stem; leaf discolorationSevere
Flowering10.51-.5460-7130°FFloret sterility; white awns or white spikes; damage to lower stem; leaf discolorationSevere
Milk11.17528°FWhite awns or white spikes; damage to lower stems; leaf discoloration; shrunken roughened or discolored kernelsModerate to severe
Dough (11.2)11.28528°FShriveled discolored kernels; poor germinationSlight to moderate
*Information in this table assumes timely rainfall events occurring after the freeze event.
Frost can also impact other crops as well.  The tips of alfalfa might get frosted off but the most severe impact will be from small grains that are now for the large part in the jointing stage.
So the action is to wait and see what the plant tells you in the next week to determine if the freeze impacted the head development. If this frost continues here is a great factsheet that might prove useful. Cultural Impacts in wheat

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