May 18, 2012

News from Neighboring States

The following release is from the Kansas State University News Service.

MANHATTAN, Kan. – Wheat fields in central and western Kansas could use at least one last good rain before harvest.

“Wheat is under stress in much of western Kansas south of I-70 and west of Pratt and Great Bend,” said Kansas State University’s Jim Shroyer. “In areas east of U.S. Highway 281, there are also areas where wheat is under stress, especially on terrace tops.”

Shroyer, a crops specialist with K-State Research and Extension, said the stressed wheat is generally showing some combination of the following symptoms:

• White heads, which developed very quickly over a wide area;
• Curled and dried up flag leaf;
• Tillers that have sloughed;
• Loss of one or more small developing kernels in the spikelet;
• Poorly developing kernels, and
• Chlorotic leaves due to poor root development and nutrient deficiencies.

Shroyer noted that the stress came on quickly this year.

“There were general rains earlier in the spring, and topsoil moisture was adequate in most areas until recently. But where subsoils were very dry after last summer’s drought, the wheat needed a regular supply of rainfall events this spring to support the top growth. Where that didn’t happen, the wheat quickly became stressed, especially during the periods of extreme heat this spring – the latest being May 4-5,” he said.

Heading and grain fill is a period of high moisture use, with wheat using about 0.25 to 0.30 inches of moisture per day. If the moisture isn’t available, the wheat will show symptoms, Shroyer said. The combination of dry soils and heat, in particular, will cause heads to turn white quickly, almost overnight.

Any additional stress, such as diseases or insects, will add to the stress.

The agronomist noted that while cool weather has returned, the crop still needs another rain or two where it is dry.

“If rain comes to stressed wheat while the kernels are still in the milk stage of development or earlier, the wheat may be able to recover some yield and test weight potential as long as the flag leaves are still alive,” Shroyer said. “If the plants are under severe stress and shut down while kernels are in the early dough stage, it is unlikely that any subsequent rain will help the kernels complete their fill. This will result in a loss of yield and low test weight regardless of the weather during the remainder of the season.

Mary Lou Peter
KSU News Writer