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Corn Yields in the Midwest in 2019: A Tale of Uncertainty and Differences

Corn yield prospects vary greatly across the Midwest in 2019.  It is a tale of delayed plantings nearly everywhere, but with the delays becoming much more significant in the eastern cornbelt than in the western cornbelt.  But, how do “early yield estimates” stack up against historical yields?

Iowa

A significant portion of Iowa’s corn was planted a week to two weeks later than normal.  However, growing season precipitation has been generally adequate and timely.  Temperatures have not been excessive, thus corn crop development has been “good” and “eyeball estimates” are for a near-normal crop.  Early windshield estimates have been for a slightly below trendline yield.

So, how does a 2% below trendline yield stack up for Iowa corn yield prospects.  For this analysis, I have used a 184.69 bu/acre yield for Iowa for 2019.  Figure 2 and Figure 3 show deviations from trend yields for Iowa corn and the percent deviation from trend yield.  As can be noted from the charts, there have been more above trend yields (57% of the time) than below trend yields over this 60 year period. 

A 3.77 bushel per acre reduction from trend yield (trend yield for Iowa for 2019 is 188.46 bu/acre) would be at the 35th percentile of yields over this period.  A 2% reduction from trend yield is at the 36.7 percentile of percent yield deviations from trend.  Over the past 60 years, there have been 21 times the percent yield reduction has been greater than 2%.  To put further perspective on this, 14 of the past 60 years (23% of the time) Iowa corn yields have been between -3.1% and +3.1%. 

Illinois

Illinois corn planting experienced more delays than Iowa corn planting.  Only 20% of Iowa corn was planted after June 3rd, whereas 55% of Illinois corn was planted after June 3rd.  Windshield surveys of Illinois crop conditions indicate more short, yellowed corn in areas where planting was significantly delayed.  For this analysis, I have assumed an Illinois corn yield that is 18% below trendline.

For 2019, this would be a yield of 151 bu/acre.  This would be 33.14 bu/acre below the trendline yield of 184.1 bu/acre.  If realized, this would be the 4th greatest nominal deviation from trend yield in the past 60 years.

An 18% below trend yield for Illinois would be the 8th greatest percent deviation from trend yield in Illinois during the last 60 years. 

Indiana

Corn planting in Indiana was very delayed in 2019.  As of June 3rd, only 31% of the state’s corn was planted.  A third of the corn in Indiana was planted after June 10th and 16% after June 17th.  Late planted corn can be subject to many growing season stresses including shallow rooting, heat stress during pollination, moisture shortages, etc.  All of these problems have been manifested in Indiana corn yields during the 2019 growing season. 

For this analysis, based on the anecdotal comments about crop conditions in Indiana, I am using a -25% deviation from corn trendline yield, or 129.32 bu/acre yield.  This would be 43.1 bu/acre below Indiana’s trendline yield of 172.44 bu/acre. Figure 8 and Figure 9 show the deviations from trend yield and the percent deviation from trend yield for Indiana for the period 1960 to 2019.


U.S. Corn

For  the U.S. as a whole, 2019 was a year with the most delayed corn planting on record.  One-third of the corn crop was planted after June 3rd.  Weather has been overall favorable toward corn development since planting, but the late start for a large portion of the crop suggests that yield will be somewhat below trendline. 

For this analysis, U.S. corn yield was projected to be 166.5 bu/ac. This would be 5.15 bu/ac below trendline yield of 171.6. Figure 11 and Figure 12 show the U.S. corn yield deviation from trendline and the percent deviation from trendline yield.

Conclusion

While corn planting was delayed across much of the U.S. this year, the delays in eastern cornbelt states was most pronounced.  These delays in plantings have set in place the environment for very low yields in states like Indiana, Michigan and Ohio. And significantly below trendline yields in Illinois.  But, the emergence of the western cornbelt as the predominant area for corn production and the relatively good growing conditions there mute the overall impact of poor yields in the eastern cornbelt and set up the prospects for a near-trend line or only slightly-below-trendline corn yield for the U.S. as a whole.  The delayed development of the corn crop in the eastern areas of the Midwest will likely preclude having good state-by-state yield estimates in the August crop report.  The first reliable state-by-state yield data from USDA-NASS for 2019 will come in the September report.



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