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.
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
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.
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 stage||Feekes||Zadoks||Approximate injurious temp. (2 hrs)|
|Tillering**||1-5||20-29||12°F||Leaf chlorosis; burning of leaf tips; silage odor; blue cast to fields||Slight to moderate|
|Jointing||(6-7)||31-32||24°F||Death of growing point; leaf yellowing or burning; lesions, splitting, or bending of lower stem; odor||Moderate to severe|
|Boot||10||41-49||28°F||Floret sterility; spike trapped in boot; damage to lower stem; leaf discoloration; odor||Moderate to severe|
|Heading||10.1-.5||50-58||30°F||Floret sterility; white awns or white spikes; damage to lower stem; leaf discoloration||Severe|
|Flowering||10.51-.54||60-71||30°F||Floret sterility; white awns or white spikes; damage to lower stem; leaf discoloration||Severe|
|Milk||11.1||75||28°F||White awns or white spikes; damage to lower stems; leaf discoloration; shrunken roughened or discolored kernels||Moderate to severe|
|Dough (11.2)||11.2||85||28°F||Shriveled discolored kernels; poor germination||Slight to moderate|
|*Information in this table assumes timely rainfall events occurring after the freeze event.|
**See Section 2 for more information about growth stages.