Winter wheat possesses an excellent physiological mechanism to survive the harshest of winter conditions. Overwintering or winter survival of winter wheat is a long process that starts in the late fall with decrease in daily temperatures, and is completed when it starts its regrowth the subsequent spring. Factors such as genetics, amount of snow cover or insulation, and winter temperatures can all play a significant role in the winter survival of wheat crop.
About Ice Injury
Another major factor that can have a large impact on winter survival of wheat is ice injury. Thawing of snow followed by sub-freezing temperatures in recent weeks have caused some winter wheat fields to be covered with ice and/or filled with water, especially the lower areas. Even though wheat plants generally go to dormancy with the onset of winter conditions, roots and crown (growing point) continue respiring. During this process, oxygen is used, while gases such as CO2, ethylene, and methanol are produced. Formation of ice layer often blocks gaseous exchange between the soil and air trapping these toxic gases beneath the soil surface and causing plants to suffocate and eventually die. It usually takes a prolonged period of icy conditions (3-4 weeks) for wheat plants to completely die. Freeze-thaw cycles can sometimes break the ice sheet and cause air to pass through allowing plants to respire.
Every year growers are curious if their wheat field will survive the winter; and like with any other winter injury, there is no easy way to find out if all or any wheat plants on icy patches survived. One way to find out is to inspect the field in April when the field starts to regrow with the rise in daily temperatures. Another indoor method outlined below can be used prior to April to estimate the extent of the damage in the field.
- Dig up whole plants from the suspected area at least three inches beneath the soil surface containing plant crowns.
- Bring plant samples to room temperature to thaw out.
- Wash off soil from the roots using cool water.
- Cut off fall growth to within 1 inch above the crown and roots below the crown.
- Rinse the crowns with cool water.
- Place 10 wet crowns in a plastic bag, inflate the bag, and tie shut.
- Place the bags in a lighted room, but not in direct sunlight.
- Check the crowns in two days, rinse with cool water and re-inflate the bag.
- After four days, the crown should show about two inches of new growth.
- When estimating survival, plants that do not show any growth after six days should be considered dead.
The Bottom Line
Some plants may show poor growth due to mold which may survive as injured plants or eventually die. Going out in the field later in the spring and conducting further assessment could be helpful in determining the winter kill.
Suggested Reading: Determining Wheat Damage from Ice Cover. 2007.