By Mark Weinraub
CHICAGO, Jan 3 (Reuters) - Bitter cold temperatures across the U.S. Plains early next week will put some of the dormant hard red winter wheat crop at risk of damage, particularly in drier areas of the region, meteorologists and agronomists said on Friday.
Low temperatures on Monday morning were expected to hit 5 to 15 degrees Fahrenheit below zero (minus 20.6 Celsius to minus 26.1 C) in parts of Kansas and Nebraska, cold enough to destroy some crops through winterkill.
"Snow cover will remain quite thin across much of Nebraska and north-central Kansas, and some extensive winterkill damage is likely there," said Don Keeney, senior agricultural meteorologist for MDA Weather Services. "Snow cover of 2 inches or less will offer little protection."
Hard red winter wheat, the most common variety grown in the United States, is the top choice of domestic millers for bread and exporters.
Keeney estimated that 15 percent to 20 percent of the hard red winter wheat belt was at risk of injury from the cold. Winterkill can injure wheat's crown, leaving it unable to provide nutrients to the rest of the plant.
Another forecaster, John Dee of Commodity Weather Group, said temperatures were not likely to stay cold for long enough to cause widespread damage, although he admitted isolated areas of northern Kansas and southern Nebraska were vulnerable.
The soft red winter wheat crop grown in the U.S. Midwest and typically used for cookies and snack foods was protected from the bitter cold by a deep blanket of snow that covered the region.
A global supply glut muted the impact of crop concerns on the wheat futures market, where prices trended near their lowest since May 2012.
At 10:54 a.m. CST (1654 GMT), KCBT hard red winter wheat for March delivery was up 4-3/4 cents at $6.36 a bushel. Chicago Board of Trade March soft red winter wheat, the benchmark contract typically used as a proxy for all varieties of the grain, was 3-3/4 cents higher at $6.00-3/4 a bushel.
Dry areas in western reaches of the wheat belt were the most susceptible to damage from the cold, said Jim Shroyer, agronomy specialist at Kansas State University, as temperatures fluctuated faster in arid soils.
"The wild card in this situation is soil moisture, Shroyer said. "If it is dry, I worry. If it is wet, I do not worry as much."
Shroyer said that air temperatures can be 5 to 10 degrees below zero for a day and soil temperatures will still be 20 to 25 degrees above zero. But if temperatures stay cold for more than 24 hours, crops planted in dry soils will be at risk.
"I am worried about it," said Roger May, a farmer in Oberlin, Kansas, in the northwest portion of the state. "We started with good moisture. It has kind of turned a little dry here lately. This crop is exposed out here. There is no snow cover."
May, who seeded 1,300 acres of wheat during the fall, said he has had problems in the past with winterkill to crops planted on the exposed sides of terraces, which are more vulnerable to wind.
At the end of November, the U.S. Agriculture Department said the winter wheat rated 62 percent good to excellent, up from 33 percent a year earlier. In Kansas, the largest wheat-producing state, the crop was rated 63 percent good to excellent at that time.
The USDA does not rate the crop during the winter as it is hard to assess plant health during its dormancy phase.
Farmers will not know for weeks the extent of the damage done by the cold.
If plants are killed outright, they will not turn green as the weather warms. If they are only damaged, they could turn green at first but still die as they fail to mature. (Additional reporting by Julie Ingwersen; Editing by Jeffrey Benkoe)