Don't Be Surprised If USDA Drops Final Yield Numbers

Agency failed to account for effects of heat for second year in a row.

Published on: Dec 26, 2011

With egg on their face after the second-largest prediction error in history in 2010 for the 2010 corn crop, based on the August estimate to final numbers for 2010, USDA didn't bat an eye and relied on its same methods to estimate rules in 2011 that it used in 2010, without adjustments.

And for the second straight year in a row, Mother Nature is making USDA look like it doesn't have estimation down to a science. The overall yield has been dropped by several bushels per acre and individual yields, especially in states like Indiana, have been dropped even more. Once again, it appears that high nighttime temperatures during the critical reproduction and grain fill period went unnoticed by USDA. Once again, several believe it's one of the reasons why USDA overestimated the crop again this August, much like it did one year ago.

Arlan Suderman, market analyst for Farm Progress Companies, expects USDA to lower their estimates at least somewhat when the final estimate numbers for the 2011 corn crop are released in early January. He has become a big proponent of the theory that high nighttime temperatures during the critical period for corn robs the crop of energy that would otherwise find its way into the ear in the form of starch that adds to kernel weight. Instead, it's burned up as part of respiration as the plant doesn't have the chance to cool down properly at night.

It may be hard to separate the impact of high nighttime temperatures on as many as 23 days straight of 90 degree or higher daytime temperatures recorded in parts of the Corn Belt. That was a record, breaking records for most consecutive days of 90 degrees or higher set in the hot decade of the 1930s.

There is still no indication that USDA intends to revamp its estimation procedure before the next season. Their method assumes normal temperatures and precipitation after each estimate is taken. When temperatures deviate to the high side, as they did for the past two years after the August estimate, final yields can tumble much farther than USDA models seem to be able to project until after harvest is complete and the corn crop is in the bin on farms or in storage at elevators.