Record Average Temps in December
With the 5th warmest November on record followed by the warmest and wettest December on record it has many of us wondering how these crops will make it through the winter. For the most part winter hasn’t been bad on these crops.
Alfalfa was Prepared
Now let’s talk about alfalfa. Alfalfa starts to harden or prepare for winter when the crown temperature reaches 60 degrees. Hardening actually increases by the fluctuating temperatures of daytime highs around 50 degrees and the lows near freezing. Looking back at November and December of 2015, November daytime temperature averaged 49.6 degrees with 15 nights at or below freezing and December averaging 42 degrees with 22 nights at or below freezing. This weather should have allowed the alfalfa plant adequate time to prepare for its winters nap and stocked the cellar with enough food to get it through winter. December 28th and 29th blessed us with a nice blanket of snow to keep our alfalfa plants tucked in tight. So what do we have to be concerned about? Fortunately there was little to no frost in the ground at the time of the rain.
As we lose our snow cover, some fields will have or had ponding. What is the fate of alfalfa there? Injury can occur in 1 to 3 weeks. Death is possible if flooded for 2-6 weeks. If 6-8 inches of growth was left in fall, this can reduce the chances of ice sheets forming and provides a little insulation to protect those crowns. Heaving is another concern in alfalfa, which normally occurs on heavy soils that have high moisture content, in which we have plenty of moisture. Repeated freezing and thawing causes the soil to expand and contract thus pushing the tap root out of the soil. Tap roots that are pushed out of the ground 1.5 inches or more will likely have broken taproots and will suffer damage from harvesting equipment. These fields will be better off terminated and rotate to a crop like corn.
In 2015, the winterkill in Minnesota and Wisconsin was caused by crown temps below 13 degrees according to Dan Undersander, UW Extension Forage specialist. Our snow cover protected us from these issues and also, our average lows rarely reached those temps.
The last thing to ponder on is the fact that our snow cover blanket is gone now exposing our alfalfa plants to the elements. Hardened alfalfa crowns and roots can be injured when air temperatures drop below 0. When temperatures rise to the 50 to 60 degree mark and the soil temperature at the 2 to 4 inch soil is 40 degrees or more for several days alfalfa will start to break dormancy. When this happens the alfalfa plant opens up its cellar doors and eats the last of its winter reserves to fuel the plant for new growth from the crown.
Modest temps in November and December allowed our wheat to tiller and grow late into the fall. This helps increase the head count for this season. However, it also exposes us to a greater risk of freeze damage on exposed tissue. Early observations look good. Very little freeze damage is observed due to the snow cover protection. Localized pockets of water and ice have been observed. However, widespread winterkill is unlikely at this point.
According to Phil Needham, of Needham Technologies, planting wheat 1” deep protects the crown. It also promotes the plants to all emerge uniformly due to consistent moisture and temperatures. Uniform emergence makes for uniform heading. “High yields come from uniform fields.” Making the field level and firm before planting allows for a uniform emergence.