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Released: February 03, 2003 Winterkill May Be Problem in Some Kansas Wheat MANHATTAN, Kan. – Dry soils and broad temperature swings may be setting the stage for winterkill in the Kansas wheat crop, a Kansas State University agronomist said. "Normally, we worry about winterkill when soil temperatures fall below 10 degrees F at the [plant’s] crown level, even if we have good soil moisture," said Jim Shroyer, who is a crop production specialist with K-State Research and Extension. This winter, however, soil is dry through much of Kansas, which could make the situation worse. Soil temperatures at depths of 2 inches have not fallen into the single digits yet, he said. But given that the crown of a wheat plant is only 1/2- to 3/4- inch deep and with the soil as dry as it is, it’s possible that temperatures around the crown have dipped into single digit territory. Soil moisture would help, because it buffers the effect of rapid drops in temperature. Some growers have wondered if the wheat has really been dormant because mild temperatures have prevailed much of the winter, but Shroyer believes the Kansas wheat crop has been dormant. "What concerns me about this latest cold spell is that we had near record highs [temperatures] just before it," Shroyer said. The wide, but quick temperature swings are hard on the crop, he said. People wonder how they can tell if their wheat has been hit by winterkill. "You can’t tell immediately," the agronomist said. "We’ll just have to be vigilant and watch as the wheat breaks dormancy to see how it looks." In cases of outright winterkill, the wheat dies while it’s still dormant and will never green up. Outright winterkill most often happens on ridge tops, terrace tops and north-facing slopes – anywhere that would be drier and colder than the rest of the field, he said. It doesn’t typically happen to an entire field, although it can if the conditions are extreme enough. There are also instances when the wheat starts greening for two or three weeks, but then starts dying. "We sometimes get calls from growers saying ‘My wheat’s going backwards,’" Shroyer said. In those instances, what likely happened is that the crown root and vascular system were damaged by dry, cold conditions. The wheat was able to green up because of the nutrients that were stored in the crown before it went dormant. But when those nutrients were used up, the plant wasn’t able to take in new ones because of the damage to the vascular system. Heaving shouldn’t be much of an issue this year, the agronomist said, as there is not enough moisture in the soil to spark the destructive process. "I am concerned about wheat breaking dormancy and starting to grow without enough soil moisture," Shroyer said. "Then it’s extra vulnerable to rapid drops in temperature – that’s when the noose gets tighter and tighter, basically. "We really need moisture – a good rain or better yet, snow," he said. Dry conditions and short stands in many of the state’s wheat fields this winter have also left fields prone to wind erosion, he added. -30- K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan. Story by: Jim Shroyer |