No. 8/May 15, 1998
Wheat Crop Outlook
Rain fell in Southern Illinois during much of the flowering period, resulting in wet soils and a real potential for the development of head scab. The development of the crop also slowed somewhat due to cool weather, with the result that the crop is only slightly ahead of normalheading time in much of the state. Head numbers appear to be reasonably good, and at this point much of the crop looks to be more or less "average." The projected wheat yield that was released this week is for an average yield in Illinois of 54 bushels per acre, which if realized would be a few bushels above the 10-year average.
One of the concerns with the crop currently is the high temperatures that are occurring this week. Wheat is a cool-season crop, with ideal daytime temperatures in the mid-70s, and nighttime temperatures in the low 50s. When temperatures rise much above this, the crop will do much more respiration than normal, losing valuable carbohydrates in the process anddecreasing the amount of carbohydrates available to fill grain. The high nighttime humidity that accompanies higher temperatures can also help diseases to spread. Also, higher temperatures cause more rapid loss of N from wet soils and will often affect root function negatively.
The appearance of the leaves can provide some idea of the effect of high temperatures on wheat. Leaves that are not a healthy shade of green are not functioning at maximal rates, and yield may suffer as a result. I have observed some decrease in "greenness" of leaves in the past week, and it may be difficult for plants to recover from this to produce high yields. There isn't much we can do about this except hope for cooler, drier weather.
Emerson Nafziger (email@example.com), Department of Crop Sciences, (217)333-4424