Even after USDA overestimated the corn crop in 2010 by more than 10 bushels per acre in the August 2010 report compared to the final production estimate for the crop, a record or near-record in terms of inaccuracy, procedures weren't changed in how to assess and estimate yields for that first report, notes Greg Preston, state statistician with the Indiana Ag Statistics Service, based in West Lafayette.
Just as last year, the August report, which assessed conditions as of Aug. 1, 2011, assumed normal weather for the rest of the growing season. Data for Indiana was taken from about 700 written surveys and about 300 plots visited by field enumerators. These are the people who visit fields and make counts. However, for the August report, there are typically no ears to count or check. They return to the same exact spots a month later in preparing for the September report. At that time, there should be ears to check and measure.
One factor many thought contributed to such a low accuracy level last year was that there were very high night-time temperatures during grain fill. USDA's formulas didn't account for that. When there are high nighttime temperatures, instead of resting and turning sugars made during the day into starch that enters the kernel, corn plants continue to respire, using up energy collected during the day.
No adjustments were made for this phenomenon for this year as far as Preston knows. However, as always, they do have a chance to send in comments and recommendations to the officials that put together the final report when they send their data. Preston indicates that due to the wet start and all the heat, his staff suggested that perhaps the Indiana yield should be trimmed a bit. He says it's possible this accounts for a yield estimate that's one to two bushels per acre than it might have been based on raw numbers collected through the formula. However, there was not a major adjustment.
That's important since high nighttime temperatures returned again, existing during most of the record-breaking 23-day streak of 90 degrees or higher in central Indiana. The crop may have not been as deep into the grain fill period a the time, although Bob Nielsen, Purdue corn specialist, says that corn planted three weeks behind is only one week behind in grain fill. The extremely hot temperatures in July and early August shoved along maturity. That's good in terms of harvesting corn that's not excessively wet, but it may not be so good when it comes to yields.