Ag Weather Forum

Early Corn Model Cautious on Yield

Bryce Anderson
By  Bryce Anderson , Ag Meteorologist Emeritus
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The first run of the UNL Hybrid-Maize model for the 2018 indicates mostly below-average yields for non-irrigated locations in the Corn Belt. (University of Nebraska-Lincoln graphic)

Projections are starting to come forth regarding how the 2018 U.S. corn crop will perform. Yes, it's early, but the numbers are starting to be crunched. At the University of Nebraska-Lincoln, a yield forecast model called Hybrid-Maize was run for the first time this season, and the results offer some caution about whether this year's crop can exceed trendline. A description of prospects in the mid-July run of the model is contained in the following excerpts from the UNL Cropwatch report issued Friday, July 13.

"Simulations of 2018 end-of-season corn yield potential and real-time crop stage were performed on July 11 for 41 locations across the U.S. Corn Belt using the UNL Hybrid-Maize crop model in collaboration with faculty and extension educators from 10 universities ...

The season started with warm conditions throughout the Corn Belt, with air temperature averaging 4 degrees Fahrenheit above normal. In contrast, rainfall was more erratic, with most locations exhibiting near- or above-normal records, except for sites in Michigan, Missouri, and Kansas with below-normal rainfall. The states experienced near-normal temperatures in the last month (June 17 to July 17). Rainfall was highly variable across locations, with above-normal rainfall in Indiana and Ohio but below-normal rainfall in Nebraska, Iowa, and North Dakota."

"Corn has reached silking in most parts of the Corn Belt, except for the northern fringe of the region where corn is still in the vegetative stage (North Dakota, Minnesota, Michigan, northern and western Nebraska, and a few scattered locations in northern Iowa, Indiana, and Ohio). Sites in the southern fringe of the region (Missouri, Kansas, and southern Illinois) are well ahead of the rest of the locations and are already in the grain-filling stage."


"It is still too early to visualize clear trends, though there is a relatively high probability of near-average yields for all sites (and even above-average yields for the sites in western Nebraska). Weather conditions during the rest of the growing season will determine if most irrigated sites will have near-average yield potential. The chance of below-average yield appears to be small for all irrigated sites but one," Beatrice, Nebraska. (Note that only western Nebraska sites are described as having prospects for above-average yields.—BA)


"Forecasted yield potential is highly variable across rainfed sites. There is a high probability of above-average yield (greater than 75 percent, or a chance of three out of four) at eight sites in northeastern Nebraska, southern Minnesota, southwestern Iowa, central Illinois, and Michigan. In contrast, there is a high probability of below-average yield for four sites along a transect that includes northeastern Kansas and portions of northern Missouri, and for the North Dakota site. Near-average yields are likely in central Iowa. The scenario is less clear for the other rainfed sites."

The discussion concludes by noting that there is still a long way to go in the 2018 season. For irrigated corn, "This can change depending upon temperature during the next two to three weeks." And for non-irrigated or rainfed corn, "Temperature and rainfall during the rest of July and early August will likely determine the trend ..." Which, of course, makes a cooler pattern for the last part of July very important.

The full article, along with more graphics, is at this link:…


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