In its latest crop condition and progress reports, USDA noted the U.S. corn harvest was 22% complete, up a mere 7% from the prior week.
The severe winter storm in much of the NW Corn Belt undoubtedly slowed progress; this compares to 38% harvested as of October 13 last year and the five-year average of 36%.
We recall that last year's rain delayed harvest is one of the reasons why the 2018 U.S. corn yield fell by 4.3 bushels per acre, so we were curious whether a drawn out harvest will lead to late season yield declines with perhaps more of the crop subject to weather damage from snows, winds and/or freezing temperatures.
This graphic shows the days after October 1 50%, 70% and then 90% of the U.S. corn crop was harvested on the left hand axis vs. the change in the U.S. corn yield in bushels per acre (bpa) on the right hand axis from the October to the January crop production report.
Firstly, the average dates for the 50%, 70% and 90% harvest complete levels to be hit are 21 days after October 1 (or October 22), 30 days after October 1 (or October 31) and 45 days after October 1 (or November 14th).
The trend for these levels are also lower implying that harvest proceeds quicker now than in the past, likely due to enhanced machinery.
The three late years that really stand out are 1985 when 50% was harvested October 30, 70% by November 8 and 90% was harvested by December 12, yet yields that season rose by 2.9 bpa from the Oct to the Jan report.
1992 also stands out with 50% harvested by November 8, 70% by November 23 and 90% was harvested by December 15, yet yields that season rose by a huge 7.6 bpa from the Oct to Jan reports.
Finally 2009, when 50% was harvested by November 14, 70% by November 24 and 90% was harvested by December 10, yields that season rose by a 0.5 bpa from the Oct to Jan reports.
Interestingly, years where harvest progress was the fastest such as 1987, 1991 and 2010 all showed yield declines from October to January.
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