Except for heavy rains in some areas, spring weather has been decent for the Illinois wheat crop. But crop ratings continue to be rather mediocre, with less than half the crop rated as good or excellent as of May 15, reports Emerson Nafziger, University of Illinois Extension agronomist.

"Wheat had a tough start in the dry soils last fall and though it survived the winter quite well, the unevenness of emergence carried over to this spring with many fields showing unevenness in plant size," he said. "Heavy rainfall and standing water in April also may have compromised the root systems to some extent and may have resulted in some loss of nitrogen."

The cool weather has also delayed heading slightly, which might prove to be an advantage if it flowering takes place under drier conditions, he said. Flowering usually takes place a few days after heads emerge, and is indicated by the appearance of anthers outside the head. Under cool temperatures, the interval between heading and flowering is longer.

"All else being equal, we prefer early rather than late heading, both for earlier double-cropping and also because an earlier start to grainfilling means less chance of weather-related problems in June," Nafziger said.

Areas of fields with later-developing plants often show reduced tillering and lower head numbers. Generally, growers estimate yield potential by counting heads per square foot and taking that number as equal to the number of bushels per acre the crop will produce, he said.

If the crop emerged late last fall or even early this spring, it did less tillering than normal. So if there are 20 plants per square foot and each produces only two tillers with heads, yield potential may be about 40 bushels per acre.

"If the main problem is low head numbers due to less tillering, head size will increase somewhat in response to the lower number of heads," Nafziger said. "This can mean higher yields than we might estimate by the head count."