1. 172. That is the number that I could not stop thinking about last night. How in the world could the US average corn yield be that low? First off, there is the possibility that the USDA is underestimating yield. But I don't think that is the right way to think about it.

2. Basis has been screaming all Fall that the crop was not there. And now the USDA has confirmed a much smaller crop size. So I start by assuming that 172 bpa is the best possible estimate of the 2020 crop yield.

3. So, how in the world did we get 172 if that is indeed the right number? Lets start with weather. In my classes here at the UI I teach me students that the golden number for IL ag is 4" of rain in July. Get that and we have a good crop. 5.4" in Jul 2020. Perfect.

4. It was dry in IA in July, but overall the state had 3". Not good but not terrible either. IA was really only state that had bad July weather. It did then get very dry in August for much of the Corn Belt. But that normally is not a big factor in corn yields. Not this big

5. If dry weather was the culprit for low corn yields, then why did soybean yields hold up better to the dry August weather? That is supposed to be the most weather sensitive period for soybean yields and we ended up above 50bpa for national average.

6. There was one weather event in August of course that has to be part of the explanation: the derecho. IA coming in at 178 certainly was impacted by derecho, probably IL below 200 as well. So that might have dropped national avg yield a bushel or two.

7. Crop condition ratings missed the corn yield too. My calcs indicate final G+E ratings were 6-7 points too high relative to 172bpa. So we can't just blame USDA yield forecasters. Crop condition raters made the same mistake.

8. So something extraordinary seemed to happen to US corn yields in 2020. I wonder if the biggest factor was COVID and low prices last spring leading to lower input use by farmers. We should not forget just how bad things were last spring. Lockdown. Economy crashed.

9. Very low corn and soybean prices persisted well into mid-August. Who was going to plant corn at the highest population rates and use the highest nitrogen rates under those circumstances? Normally, I don't put much stock in this kind of explanation, but 2020 was not normal!