Kentucky Corn Planting Progress does not Explain Corn Yield
Chad Lee, University of Kentucky
Corn planting is on everyone’s mind as corn planting progress is as late this year as it has been in a long time.
The Week #16 corn planting progress was only 10%, but corn planting progress reports from 2001 to 2021 show very little correlation between planting progress and yield. Let’s get to the some of the erratic planting patterns we have observed and then we will get back to those correlation.
Wild Swings in Corn Planting Since 2008
Since 2001, corn planting progress for the Week#16 report has been below 20% nine springs, with all of those occurring since 2008. Corn planting progress has been at 60% or above four springs. The highest planting progress rate occurred in 2012 which also had the severe drought and the lowest corn yields.
Poor Correlation Between Planting Progress and Corn Yields
RELAX.
Corn planting progress in these reports have very little correlation to corn yields at the end of the season. Graphs with blue circles include corn planting progress for Weeks #15, 16, 17 and 18 compared with corn yields for 2001 to 2021. Corn with green circles include the same comparisons, except that 2012 is removed.
With 2012 included the correlations between corn planting progress and corn yield are stronger with r-square values ranging from 0.44 to 0.32. In all those comparisons, the 2012 season pulls the yields down when more acres are planted early. Again, 2012 had the highest planting progress for most weeks and the lowest yields of any year.
When 2012 is removed correlations between corn planting progress and yield become weaker with r-square values ranging from 0.11 to 0.185. With these weak correlations, the weak trend suggests that more planting progress in weeks 15, 16 and 17 result in lower corn yields.
Week #18 gets interesting. For Week #18, corn planting progress between about 40 and 60% resulted in highest yields most often whether 2012 is included or not. Again, these correlations are weak. If anything, they confirm that many other factors besides planting date are important for corn yields. I would suggest that these correlations support that field conditions and weather are more important than calendar for planting corn. Still, it will be fun to see what the Week #18 report tells us.
