Warm Temps, Snowfall, and Spring Assessment – Cassidy Fletcher, Northeast Agronomist and Technical Lead
Recently areas in the Northeast have experienced fluctuating temperatures, ranging from below freezing to up near 50 degrees. That raises the question, what is this doing to our wheat crop?
We know that wheat can withstand a lot of environmental impact. The survival of a wheat plant depends on the survival of the crown, and what temperature that crown is at throughout the course of the winter. Snow cover, in some extreme situations can act as an insulator for the crown and the ground, proving to be a saving grace. But if we don’t have factors in our favor what can we do?
When it comes to extreme cold temperatures, snow covering the wheat plants acts as an insulator and minimizes the temperature effects on the plant. A few inches of snow covering the ground and the plant allows the ground to remain wet and the temperature to remain moderate as the air temperature dips down into normally killing temperatures. However, if we see bone chilling temperatures without that insulating layer of snow, we begin to see the plants become affected and start to die off. When the ground is dry and exposed during temperature changes, there is a greater chance that the plant will show damaging effects come spring time. This is due to dry ground changing temperatures much faster than wet ground, because of the inability to regulate a slow change. This then can lead to crop injury. Extreme and quick swings in temperature can also cause issues for the plant. A period of favorable weather conditions followed by a quick drop in temperature, does not allow the plant time to regulate itself and respond according to the environment.
But what about long periods of warm weather?
Air temperatures have risen close to 50 degrees for extended periods of time so far this winter. This has caused snow covers to melt and fields to get muddy. What is this doing to the soil temperature? With the rise in temperature, we could begin seeing a decrease in winter hardiness of the wheat plants. Once the wheat plants harden, they reserve their maximum winter hardiness until the soils begin to warm up. Soils that get over 50 degrees for a prolonged period of time start to cause the plant to lose some of its winter hardiness and tolerance for cold temperatures. If the soil temperature around the crown drops back to 32 degrees and the crown hardens, it will not regain any of the winter hardiness and tolerance that it recently lost. In places where the crop was planted late, did not tiller to its full potential, or did not develop a strong root structure this swing in temperature begins to cause more issues than places where the wheat got a better and early start the previous fall. However, in order to change the soil temperatures to levels that may injure the crop and decrease hardiness, we will need weeks of warm weather. With most of the soils being wet, especially from melting snow, it will take more than a few days of sunshine to warm up the soil and crowns.
There still is plenty of chance for injury, as winter has only just begun. Freezing and thawing of the ground could heave up crowns and cause patches of winter kill. Plants with poor root systems that struggled early in the fall may see winterkill throughout the winter season.
But before we make any assumptions in the spring, it’s best to assess your fields for winter survival.
How to assess winter survival
The first and most obvious sign of winter kill is during spring greenup. Once plants begin to come out of dormancy in the spring, plants that do not green up have most likely been killed by the winter conditions. Some plants that have only been “injured” by the cold temperature may just take a while to green up. Another option that you may see is damaged plants greening up late but then slowly beginning to die and go “backwards”. These symptoms are a result of the plants not having the means to transport the needed nutrients. This could be due to injured roots or an injured crown.
If the soils surrounding the plants were dry during the winter, the plants may have desiccated and died. This is likely a result of the soil conditions rather than the cold temperatures. During the spring when the ground is thawing and unthawing, crowns can also be heaved out of the ground. The repeated process opens up the soil and slowly pulls the crown out of the plant and leaves it above the soil surface, exposing it to the environment. This can cause tremendous damage to wheat stands, causing alternative decisions to be made in the spring.
As soon as you are able to get on your fields in the spring, it is important to check stand counts and estimate total yield loss. You will want to access what is left in the field to determine fertilizer rates and total crop loss before taking any action. If there are any questions regarding stand quality or wheat assessment, please reach out to your local Territory Field Manager.