Do corn crop conditions as of mid-September for this year vs. the same time last year reflect the same percent change vs. year ago yields?
We try to answer that question in this graphic where the USDA September 2019, final 2018 and 30 year trend yields for the top 18 corn producing states and the U.S. are plotted on the left hand axis in bushels per acre (bpa).
On the right hand axis is the percent deviation of the 2019 vs. the 2018 yield, and also the percent deviation of 9/15/19 crop rating from the 9/16/18 crop rating.
Crop conditions are measured using our usual ratings system where we weight the crop based on the percent in each category and assign that category a factor of 2 for very poor, 4 for poor, 6 for fair, 8 for good, and 10 for excellent and then sum the results.
Starting with trend, only 8 of the 18 states have their yields as measured by the September 2019 crop report above their respective 30-year trend.
Tennessee leads the way at 17.6 bpa, or 11.2%, above trend as this state is the only one this year to register a record state corn yield.
Other states doing well vs. trend include CO, KY, MO and TX.
Conversely, North Carolina has an 18.1 bpa shortfall vs. trend, off 14.1%, with IN, MI, MN and OH also faring poorly vs. trend.
As for 2018 vs. 2019 in terms of yield and crop rating differences, Texas yields this year at 140 bpa are 32 bpa or 29.6% ahead of last year which corresponds well to crop ratings as of mid-September 24.4% above the mid-September 2018 condition.
MO, CO and PA also perform well in this regard, although Colorado's 13.8% rise in yields vs. last year stands in contrast to crop ratings 3.4% below year ago levels.
On the other hand, the Eastern Corn Belt states are faring the worst with IL yields off 14.3% from last year with ratings down 19.0%, IN yields down 14.8% with conditions off 22.0% and OH having yields 15.5% down from 2018 with crop ratings off 23.3%.
Note that KY and PA in addition to CO have yields higher than last year though ratings are lower with NC, ND and SD having lower yields this year despite better crop ratings.