Winter survival of wheat
Conditions have been unusually cold throughout Kansas during most of December. Also, there has been little or no snow cover for most of this period. This means that soil temperatures have been colder than normal. Will this make some wheat fields susceptible to winter die-off?
Factors to consider
The following are some of the factors to consider when evaluating the outlook for winter survival of wheat:
How well has the wheat cold hardened?
When temperatures through fall and early winter gradually get colder, that helps wheat plants develop good winterhardiness. When temperatures remain unusually warm late into the fall (which can lead to excessive vegetative growth) then suddenly drop into the low teens, plants are less likely to have had time to cold harden properly and will be more susceptible to winterkill. This fall, temperatures generally fell gradually. It did not go from unusually warm with strong plant growth to bitterly cold in a single day. As a result, the wheat should be adequately cold hardened in most cases.
How well developed is the root system?
Good top growth of wheat doesn’t necessarily indicate good root development. Poor root development is a concern where conditions have been dry. Where wheat plants have a good crown root system and two or more tillers, they will tolerate the cold better. If plants are poorly developed going into winter, with very few secondary roots and no tillers, they will be more susceptible to winterkill or desiccation, especially when soils remain dry. Poor development of secondary roots may not be readily apparent unless the plants are pulled up and examined. If plants are poorly developed, it may be due to dry soils, poor seed-to-soil contact, very low pH, insect damage, or other causes.
How cold is the soil at the crown level?
This depends on snow cover and moisture levels in the soil. Winterkill is possible if soil temperatures at the crown level (about one-half to one inch deep if the wheat was planted at the correct depth) fall into the single digits. If there is at least an inch of snow on the ground, the wheat will be protected and soil temperatures will usually remain above the critical level. Also, if the soil has good moisture, it’s possible that soil temperatures at the crown level may not reach the critical level even in the absence of snow cover. But if the soil is dry and there is no snow cover, there may be the potential for winterkill, especially on exposed slopes or terrace tops, depending on the condition of the plants.