Lebanon Crop Management Video

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09 January 2014

The Affect of the Recent Cold Weather on Winter Crop Stands

Del Voight - Penn State Extension
 The recent cold snap that recorded extremely low temperatures and wind chills coupled with minimal snow cover and wet water logged soils from the thaw prior to the quick drop in temperature is of concern this winter for small grains and alfalfa.
Alfalfa
Dr. Marvin Hall recently related some key thoughts regarding the affect of the recent cold weather with minimal snow fall and wet soils.that may answer some
 questions regarding the effect of the recent cold temperatures on alfalfa survival.

Ø  The buds (formed last fall and are normally be the location of growth this spring) on the crown of alfalfa can withstand temperatures of about 5° F before they start to die.
Ø  Dormant growing tissue on the crown (not formed into a bud yet) can withstand temperatures of about -10° F before it starts to die.
Ø  Snow and soil insulate against the cold air temperatures reaching the buds or other growing tissue on the crown.
Ø  Depending on the amount of snow cover and the water content of the soil it can take a long period of extreme cold before temperature at the alfalfa crown (2-3 inches below the soil surface) become deadly for the alfalfa.

Small Grains
While Winter Wheat is pretty hardy it can have winter injury particularly where wet soils exist.  With little snow cover and the alternating freeze and thaw that we have experience we could see some heaving on the later planted fields.  It will be important to assess stands as green up occurs to assess the how severely the wheat may have been impacted. most wheat is in the tillering phase so we could see some burning and affect the ability of the plant to tiller.  The return to above normal temperatures may aid this however it is unknown how much this will be affected. Assessing wheat now to determine top dress during the next period of open and moderate temperatures is essential.

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.
**See Section 2 for more information about growth stages.


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