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Wheat specialist gives tips on evaluating potential for winterkillKansas Frigid temperatures arrived with a vengeance in Kansas in mid-December which may have prompted wheat growers to wonder if that is causing any winterkill of wheat? There are three main questions to consider when evaluating the potential for winterkill, said Jim Shroyer, K-State Extension agronomy state leader and crop production specialist. --How well has the wheat hardened off? When temperatures through fall and early winter gradually get colder, that helps wheat plants develop good winterhardiness, Shroyer said. "When temperatures remain unusually warm late into the fall then suddenly drop into the low teens, plants are less likely to have had time to harden properly and will be more susceptible to winterkill," he said. "This fall, temperatures have fallen off gradually and the wheat crop should be adequately hardened in most cases." --How well developed is the root system? Where wheat plants have a good crown root system and two or more tillers, they will have better winterhardiness, Shroyer said. If plants are poorly developed going into winter, with few secondary roots and no tillers, they will be more susceptible to winterkill or desiccation. "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 poor seed-to-soil contact, dry soils, very low pH, insect damage, or other causes," he said. --How cold did the soil get 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 inch deep) get down to 10 to 12 degrees or less, Shroyer said. 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 in low-lying areas, depending on the condition of the plants. Air temperatures below -10 degrees can certainly reduce soil temperatures below critical levels when the soil is dry and there is no snow cover," he said. To test for winterkill damage, producers can dig up a few plants, put them in pots, and bring them inside to warm up, the K-State agronomist said. If the plants do not respond to the warmer conditions, they may have suffered winterkill injury. "If plants are killed outright, they won't green up," Shroyer added. "But if they are only damaged, it might take them awhile to die. They will green up and then slowly go "backwards" and eventually die. There are enough nutrients in the crown to allow the plants to green up, but the winter injury causes vascular damage so that the nutrients that are left cannot move, or root rot diseases move in and kill the plants. This slow death is probably the most common result of winter injury on wheat." Direct cold injury is not the only source of winter injury, he added. "Under dry conditions, wheat plants may suffer from desiccation," he said. This can kill or weaken plants, and is actually a more common problem than direct cold injury." 12/22/08 Date: 12/18/08 Advertisement
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