Hard freeze could damage Kansas wheat
The hard freeze throughout Kansas in the early morning hours of April 15, could cause some damage to wheat, said Jim Shroyer, K-State Research and Extension crop production specialist. Wheat in the jointing stage is most at risk, he said.
There are a number of key factors in determining freeze damage: the stage of development of the wheat, the density of the stand and condition of the plants, the amount of residue on the soil surface, the extent and duration of low temperatures, temperature gradients within the field, soil moisture, and the wind speed, Shroyer explained.
* Stage of development. Wheat that hasn’t started to joint yet might suffer damage to the existing foliage, but the growing points will be protected by the soil and should escape injury. This wheat will have cosmetic damage to the leaves that will show up almost immediately. Jointing wheat can usually tolerate temperatures in the mid to upper 20′s with no significant injury. But if temperatures fall into the low 20′s or even lower for several hours, the lower stems, leaves or developing head can sustain injury.
* Density of the stand and condition of the plants. If the stand is thick, that will tend to reduce the extent of freeze damage as the warmth of the soil will radiate up into the canopy. On the other hand, well-fertilized succulent wheat has often sustained more freeze injury than wheat that is not as well fertilized. Thin stands, which are common this year, are at higher risk of injury because the air can penetrate the stand more easily.
* Residue. Many times there is more freeze damage in no-till fields because the residue acts as a blanket and doesn’t allow the heat from the soil to radiate up into the plant canopy.
* Extent and duration of low temperatures. Significant injury becomes much more likely if the temperatures in the damaging range last for two hours or longer.
* Soil moisture. There is often less freeze injury at a given temperature when soils are wet than when dry. Wetter soils tend to radiate a little more warmth than dry soils.
* Wind speed. Windy conditions during the nighttime hours when temperatures reach their lows will reduce the amount of warmth radiating from the soil and increase the chance of injury.
* Temperature gradients within the field. Low spots in the field are almost always the first to have freeze injury. The coldest air tends to settle in the low areas, especially under calm wind conditions.
There are many possible scenarios after a freeze, and things do not always go according to “the book,” Shroyer said. He advised producers to keep watching their fields closely over the next 7 to 10 days for the following:
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