Soil temps reach critical point for winter wheat
The recent cold weather has growers concerned about the health of their winter wheat crop, according to Joel Ransom, North Dakota State University Extension Service agronomist for cereal crops.
“With 700,000 acres planted this fall, which is the most winter wheat acres since 1985, the potential impact on the winter wheat crop in the state is not trivial,” Ransom says. “The critical temperature for our most winter-hardy winter wheat varieties is about minus 4 degrees F, while varieties developed in states to the south of us can be injured when temperatures dip below 14 degrees.”
Although air temperatures have been below these critical values, it is the soil temperature around the crown of the winter wheat plant that is important. Soils retain a great deal of heat, so soil temperatures lag behind those of the air.
Snow cover insulates the soil and is very important for the survival of winter wheat crops during most years. With little or no snow earlier this year, soil temperatures were getting low enough in some areas of the state to cause concern, particularly if the variety sown was not one of the most winter-hardy types.
In addition to variety, the size and health of the plant can impact how well the crop will tolerate the cold.
“Generally, plants that have four or more leaves in the fall can withstand a more prolonged period of cold than smaller plants because they have more reserves in their crown,” Ransom says. “Fields that have a history of no till and have a good level of crop residue from the previous season may insulate the soil to a degree, much like snow cover.”
Based on U.S. Department of Agriculture data, the success of a crop of winter wheat making it to harvest in North Dakota has been fairly high. During the past 50 years, the percentage of the planted acres that were not harvestable averaged only 6 percent.
“This does not mean that there isn’t a risk,” Ransom says. “During that 50-year period, there were several years when losses were approximately 40 percent of the acreage.”
The recent snow and the warmer weather is great news. Until the recent cold snap, the mild weather has been a positive for winter wheat because prolonged cold probably is more damaging than a brief but very cold period.
“We sampled our winter wheat field just before last week’s cold weather and found excellent vigor and regrowth, which indicates that the crop has not been damaged as of yet,” Ransom says. “For growers who are curious about the viability of their winter wheat crop as spring approaches, dig up several seedlings throughout the field and put them in a plastic bag with a bit of water, close the bag and leave them at room temperature. After a few days, viable plants should begin to grow. We plan to demonstrate these procedures at our Best of the Best meetings scheduled for Feb. 7 in Dickinson and Feb. 8 in Minot.”