Fundamentally Speaking
Joel Karlin DTN Contributing Analyst

Wednesday 08/27/14

IL July Temps vs. Corn Ear Weights

Last week's Pro-Farmer crop tour while noting record U.S. corn yield potential was unequivocal in saying that Illinois has the best looking crop in the country with its' estimated state yield at 198 bushels per acre (bpa).

This tops the USDA August 2014 Illinois yield estimate of 188.0 bpa though this projection like the national one is expected to increase in subsequent crop reports.

They pointed to ideal conditions throughout the growing season resulting in a massive crop that should have no problems holding onto yield potential into harvest.

If this is the case, we suspect that the very cool temperatures that were seen in July contributed to their fantastic corn yields.

Work we have done in the past suggests that while July rainfall is key to corn yields as it goes through its critical pollination period, July temperatures may be even more important especially if subsoil moisture reserves are adequate as was the case this year.

This graphic is a scatterplot showing the implied ear weight of Illinois corn vs. average July temperature in degrees Fahrenheit.

The chart shows generally higher ear weights are associated with cool July temperatures and vice-versa.

The r squared indicates that about 57% of ear weight variability is explained by July temperatures.

The July 2014 average Illinois temperature was 70.4 degrees, the second coolest ever since 1895 with only 2009's 70.3 degree reading cooler.

All season we have noted how the 2014 U.S. corn crop is shaping up similar to the record yield seasons of 1994 and 2004.

Though the Pro-Farmer three year average tour data does include the 2012 drought year, average ear counts this year are 11% above the average, grain length 18% above and ear girth 4% better.


Posted at 8:46AM CDT 08/27/14 by Joel Karlin
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