Sep 20, 2014
Home| Tools| Events| Blogs| Discussions Sign UpLogin

Chip's Chore Time

RSS By: Chip Flory, Pro Farmer

Chore time for me isn't what it used to be when I was growing up on our eastern Iowa farm. In fact... I don't even have horse chores to do any more!

Changes for 2008 Pro Farmer Midwest Crop Tour

Aug 11, 2008

Chore time for me isn't what it used to be when I was growing up on our eastern Iowa farm, but taking care of two horses in the morning before I head in for work gives me a little time to think about the day ahead. Each morning, stop at this spot to get a feeling for the "tone of the day" - and some attitude about agriculture and the markets.

I was thinking…

... about an important change we're making for the 2008 Pro Farmer Midwest Crop Tour.

We're changing the yield calculation -

As we announced after the 2007 Midwest Crop Tour, we are changing the yield calculation. The only reason we can do this is because the new calculation uses the same data to generate yield estimates as the "old" calculation. That allowed us to "recalculate" yields and to generate "new averages" from past Tours (using the new calculation) for legitimate year-to-year comparisons.

The change does not mean past Tour data was "worthless." If used properly, it was exceptionally valuable. We've stressed many times to compare year-to-year changes in each state's Crop Tour yield estimate... and not to compare Crop Tour estimates to USDA estimates. By comparing the results of one Tour to the next, we've been able to identify year-to-year trends in each state and for the U.S. corn crop. That is still the "instructed use" for the new Crop Tour calculation. Pegging the final yield in each Tour state during the third week of August is a "bit much" to ask... but we will be confident in yield trends revealed on the 2008 Midwest Crop Tour. And, just as with the "old" yield calculation, the "new" yield calculation has a "historical error" that must be considered.

So... why make the change?

Because, on average, the new calculation generates a yield estimate much closer to final state yields. "Old" Crop Tour yields were generally way below "realistic" yields and the big upside adjustments we made to Tour results for the Pro Farmer yield estimates caused serious confusion. The historical error of the new yield calculation means we'll still make adjustments... but those adjustments will likely be much less than in the past.
Of course... there are exceptions. And, unfortunately, we're going to sacrifice accuracy in Minnesota for closer pegs in other Tour states.

"Old" versus "new" Crop Tour yield calculation
(avg. error, 2001-2007, Tour yield compared to USDA final)

calculation was
calculation is
Ohio 15.44 bu. too low 4.72 bu. too low
Indiana 16.10 bu. too low 3.41 bu. too low
Illinois 10.21 bu. too low 4.29 bu. too high
Iowa 20.00 bu. too low 5.82 bu. too low
S. Dakota 5.86 bu. too low 5.27 bu. too high
Nebraska 28.12 bu. too low 16.31 bu. too low
Minnesota 1.71 bu. too low 12.09 bu. too low
Average of all sample from all seven Tour states compared to USDA final national yield 7.68 bu. too low 5.48 bu. too high

Look at the "U.S. final" comparison... how could the average yield of all samples from Ohio, Indiana, Illinois, Iowa, S. Dakota, Nebraska and Minnesota be (on average) below the national average yield!?! That just doesn't make sense! The new calculation - using the same base data - generates a much more sensible yield for these normally higher-yielding Corn Belt states.

In Illinois, we don't scout lower-yielding acres in "far-down-state" - that pushes the historical error from "too-low," to "too-high." We also scout the highest-yielding areas of Minnesota and S. Dakota. The new calculation gets closer in Nebraska, but is still well below USDA's final because scouting is concentrated in dryland areas.

There was one year when the "old" calculation worked better than the "new" calculation. In 2003, slightly behind-average development left the crop vulnerable to the August drought and the poor finish. But... it was not late development that allowed the "old" calculation to zero-in... it was the poor finish. In late developing years with a "good" or "excellent" finish, the "new" calculation has been more accurate.

The 2008 crop is vulnerable to a 'poor' finish -

Late development has left the 2008 corn crop vulnerable to a poor finish. We know that. That's why we'll be quick to adjust crop estimates if the growing season ends early.

Log In or Sign Up to comment

COMMENTS (4 Comments)


Could you please post your corn calucation formula. I have yet to find it. Thanks.
5:03 PM Aug 29th
I am wondering this year in Iowa. Will you drive past the drown out and replants to find more mature corn and soybeans to check for yield or will the cars stop occasionally at a zero yield spot and count some of those.
9:19 AM Aug 19th
The Home Page of Agriculture
© 2014 Farm Journal, Inc. All Rights Reserved|Web site design and development by|Site Map|Privacy Policy|Terms & Conditions