No 'Magic Formula' for yield (or demand... or price!)
May 17, 2013
From The Editor
May 17, 2013
Hello Pro Farmer Members!
I never realized how many people were experts at estimating corn yields at this time of the year! I'm not... I try to estimate yields at this time of the year but when I do it, I fully realize I'm likely wrong. Things change... and we've only really got two pieces of a very complicated puzzle right now.
First piece: A chunk of the Corn Belt has plenty of water to get the crop started.
Second piece: Probably one-third of the crop will be planted after even the latest "too-late" dates for corn planting.
Some still stick with May 10 as the "too-late" date... that maximum yield potential can't be hit on corn planted after May 10. In my opinion, genetics have pushed that date back... a bit. Improved management has pushed the date back several days, something I think will be proven again this year. Ahead of last week's rain, most farmers stayed in control and didn't start mudding in corn. A decade ago, the mud would have been flying. Instead, most farmers waited until conditions were at least close to fit before putting seed in the ground.
Soil conditions at planting time help improve germination rates and stand... and the Crop Tour tells us plant populations have helped improve yield more than any other factor in the past 10 years. Again, that's a combination of genetics and management.
I've moved the "too-late" date to May 20 in my analysis. Corn planted before May 20 can reach its maximum yield potential... if conditions are really good for the rest of the plant's life. Corn planted after May 20 probably won't pollinate until late July... which points to a late September black layer. (The plant reaches physiological maturity about 56 days after pollination). That means the crop will still be trying to add yield when days are getting too short to gather all the energy needed.
After the May 10 S&D Report that included USDA's first official yield projection of the year, it was amazing how many "sure-fire" yield models circulated social media. My favorite was this: "Corn planted by May 20 = 100% trendline yield; corn planted May 20 to June 1 = 90% trendline yield."
Some of the best perspective I've seen on the impact of late-planting was delivered this week by Roger Elmore and Elwynn Taylor from Iowa State University's Agronomy Department. We're all familiar with planting dates, analog-year analysis, and Growing Degree Days (GDD), but they used a term that's rarely heard: Stress Degree Days (SDDs). I'm a big-time believer in watching SDD accumulation. Basically, it measures how many days the crop was under stress due to a lack of moisture, high temperatures or a combination of the two.
The best example of SDDs impact on yield (in my opinion) was 1995. That year the crop was planted late due to excess moisture. Conditions after pollination were not good. Moisture stress was minimal in the first few weeks after pollination, but temperatures were hot. Above-normal daytime temps were common that year, but most important were the number of nights in which temps didn't fall below 70 degrees. That limits the plants ability to rest... and that rest break at night is when the plant turns the energy collected during the day into sugar. That sugar is turned into starch... and the more starch you can pack into the kernel the heavier the kernel weighs. Heavier kernels equals more yield.
More evidence of the importance of SDDs came in 2009. Very few SDDs were accumulated in 2009... conditions were generally cooler and wetter than normal after pollination. Plants stayed green very late into the year and kernels just kept gaining weight. Quality of the 2009 crop was poor and it refused to dry down in the field, but there were a lot of bushels! That was the result of a low level of SDDs.
That, however, doesn't mean planting date and soil conditions at planting aren't important. Now is when stand is being established and the number of seeds that successfully germinate will help determine how many ears are making grain later this year. But, what happens after pollination has much more to do with final yield than does planting date.
That's why my bottom line is this: Any yield estimate right now is just a guess. There's no "magic formula" for yields at this time of the year. Anybody that argues yield potential at this time of the year is arguing only for the sake of the argument. You can't even debate yields at this time of the year... there's just not enough information available.
And because there's no way of accurately predicting yield, there's no way of accurately predicting demand for the 2013 corn crop. In May of 2012, USDA predicted a 2012 national average corn yield of 166 bu. per acre and a 2012-13 corn carryover of 1.881 billion bushels. Those estimates were made by some of the smartest guys in the estimating business with access to unbelievable analytical firepower and they missed the yield by 42.6 bu. per acre and they overestimated carryover (as of the May 2013 S&D Report) by 1.122 billion bushels!
Oh... and USDA's May 2012 national average on-farm price prediction for the 2012-13 marketing year was $4.20 to $5.00 ($4.60 midpoint). In the May 2013 S&D Report, the average price estimate for 2012-crop corn is $6.70 to $7.10 ($6.90 midpoint).
Things change, don't they?
That's it for now...
My son Thomas' graduation reception is this weekend. I can't believe how the time has flown. (Please... save the "You're getting old" jokes...)
Follow me on Twitter at @ChipFlory
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