Ag Weather Forum

Big Yield Forecast In College Model

Bryce Anderson
By  Bryce Anderson , Ag Meteorologist Emeritus
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The latest corn yield projection from a yield-modeling project headquartered at the University of Nebraska-Lincoln calls for mostly above-average yields, except for the northern portion of the Corn Belt where loss due to a frost/freeze event is still possible. The report summary is included here.--Bryce

Twitter @BAndersonDTN

Grain filling continues in Nebraska and most of the Corn Belt, except for southern locations where black layer has already been reached. There were good rains the last two weeks across the entire Corn Belt and relatively lower temperatures in Nebraska and Iowa and warmer temperatures in the eastern Corn Belt, resulting in a respective increase and decrease in the risk of early-killing frost. To evaluate in "real-time" fashion the impact of this season's weather on corn yield potential, and its spatial variability across the Corn Belt, simulations of 2014 end-of-season corn yield potential were performed Sept. 12 for 25 locations using the Hybrid-Maize model.

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The Hybrid-Maize model simulates daily corn growth and development and final grain yield under irrigated and dryland conditions. The model estimates "yield potential," which is the yield obtained when the crop is not limited by nutrient supply, diseases, insect pressure, or weed competition--conditions that represent an "optimal management" scenario. It also assumes a uniform plant stand at the specified plant population, and no problems from flooding or hail. Because weather and management factors are "location-specific," Hybrid-Maize simulations are based on actual weather data and typical management practices at the location being simulated as provided by extension educators in each state.

Crops have already reached black layer at the sites in Kansas, with final simulated yield seven percent to twenty-nine percent above the long-term mean. In the other sites, median forecasted yield has changed little since the August 30 forecast and the range of forecasted yields (i.e., the difference between 75 percent and 25 percent scenarios) has narrowed because crops are approaching black layer. Therefore, we expected final simulated yields to be very close to the median forecasted value, excepted at sites where a high risk of early-killing frost can reduce significantly the grain filling duration.

Due to relatively low temperatures during the last two weeks, risk of early-killing frost has slightly increased in Nebraska and Iowa whereas warmer temperatures have decreased frost risk in Illinois and Ohio. If frost occurs, its timing will ultimately determine the magnitude of the yield impact. For example, little yield reduction is expected if frost occurs just a few days before the predicted black layer date and this may be the case for most locations across the Corn Belt. It should be noted, however, that there are other negative impacts on an early-killing frost besides yield reduction such as low test weight, high moisture content, increasing drying cost, and combine losses due to stalk breakage and diseases.

Compared with the previous August 30 forecast, probability of above-average irrigated yield in central and west Nebraska has increased. Thus, above-average irrigated yields are now expected at all sites in Nebraska, except for Concord where the probability of below-average irrigated yield due to early-killing frost is relatively high. It should be noted, however, that median irrigated yield forecasts will be within plus-or minus- 10 percent of long-term average at all sites, except for Clay Center.

The median dryland yield forecast has slightly improved since the August 30 forecast at three locations in the eastern Corn Belt (DeKalb, Ill., Custar, Ohio, and South Charleston, Ohio) due to a combination of good rains that broke a dry spell and relatively warmer temperatures that have reduced the risk of an early-killing frost. Above-average dryland yields are expected at all simulated sites across the Corn Belt, except for Sutherland, Iowa, and the two sites in Wisconsin where yields are likely to be near or below-average due to high probability of early-killing frost. It is remarkable that median dryland yield forecast is well above (greater than 10 percent above) the long-term average in 12 of the 17 sites.

Conclusions

Irrigated and, especially, dryland yields are forecasted to be above average at a majority of sites. The probability of an early-killing frost or freeze continues to be high at northern sites in the Corn Belt, with a slight increase in Nebraska and Iowa and a decrease in Illinois and Ohio during the last two weeks. It should be noted that these forecasts do not take into consideration problems with stand emergence due to residue, hail/flooding damage, replanting situations, disease, or nitrogen leaching.

Full report is at this link: http://cropwatch.unl.edu/…

(CZ)

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