USDA’s October corn yield forecast is standing, even after the agency acknowledged a processing error that affected September corn data and fueled questions about its latest estimates.
On Oct. 23, USDA’s National Agricultural Statistics Service (NASS) announced it found a processing error affecting September 2026 corn plant populations, ear counts, yields and production for Kansas and Nebraska. The error also affected September averages for plant populations and ear counts across 10 states, along with U.S. corn yield and production forecasts. However, NASS didn’t say exactly what the error was or why.
NASS says it has corrected the affected September data in its Crop Production reports and Quick Stats database. However, the agency emphasized that its October forecasts, released Oct. 9, were reviewed and validated and have not changed.
That means USDA’s latest national corn yield estimate remains 181.2 bu. per acre, up 2.74 bu. from September’s 178.58 bu. per acre. Total production remains projected at more than 16 billion bushels.
The announcement comes after USDA’s October report caught the corn market off guard, triggering a sharp sell-off and renewed scrutiny of the data behind the agency’s yield projections. But according to AgriTalk AM host and Farm Journal economist Chip Flory, who’s been pushing for answers since the October report was released, there are still major questions left unanswered after NASS issued the correction on Friday.
“The ear and plant counts in Nebraska and Kansas were incorrectly processed for the September report, according to the statement from NASS, but the processing error was not explained. While it’s a good thing NASS has acknowledged the error and issued a correction, not knowing what the error was, how it happened and how NASS plans to not let it happen again raises many more questions,” says Flory. “We will continue to ask questions that need answers in order to be confident in the process that provides critical information and data to the markets that has a direct effect on farmers’ businesses.”
Correction Comes After Pushback Over October WASDE Surprise
The correction from NASS comes after much of the national increase in USDA’s October corn forecast traces back to one state. USDA raised Nebraska’s corn yield estimate by 11 bu. per acre to 188 bu. per acre in October. But on Friday, NASS corrected the Nebraska corn yield in September to 182 bu. per acre, up 5 bu. per acre from the original report.
For context, USDA’s August forecast for Nebraska was 183 bu. per acre, so the September-to-October jump more than recovered a drop in between. The size of the increase raised questions about how Nebraska could see such a major change in a single month.
The controversy intensified after analysts examined the field sample data. In September, the data suggested 90% of Nebraska fields sampled were nonirrigated, with only 10% irrigated. In October, the balance of ear counts was more typical, with 55% irrigated and 45% nonirrigated.
The samples are collected by the National Association of State Departments of Agriculture (NASDA) for USDA’s National Agricultural Statistics Service. The shift prompted farmers and analysts to question why irrigated fields appeared to make up such a small share of the September sample.
As AgBull.com’s Jim Wiesemeyer points out, Friday’s correction only proves a processing error, not a proven fieldwork failure.
“A processing error does not establish a fieldwork failure. The notice does not identify faulty enumerator counts, inadequate training, staffing shortages or an unrepresentative sample as the cause. Those are separate issues that would require evidence. Accurate field observations can be mishandled during processing; alternatively, errors can arise elsewhere in the reporting chain. NASS has not supplied enough detail to identify the precise failure here,” Wiesemeyer reported.
How USDA Generates Yield Forecasts in October
Seth Meyer, director of the Food and Agricultural Policy Research Institute (FAPRI) at the University of Missouri, served as USDA’s chief economist for five years and is familiar with how yield data is collected. He told AgWeb earlier this month the change from September to October is built into the process.
“You’re switching from field-level counts, so they’re going out into the field and you’re getting farmer reporting,” Meyer says. “Now they’ve actually got harvest results. So you’re transitioning from pure field level without harvest for a maturing crop into a combination of that and farmers’ actual results.”
Meyer says that’s why an October yield change wasn’t a complete shock to him. Before the report, he told AgWeb USDA could surprise the market by moving higher.
“October changes in yield are not uncommon when you have that kind of transition,” Meyer says, adding that large yield changes are less common from here forward because farmers are now reporting actual yields.
However, the Nebraska sample data raised additional questions about the reliability of the September figures.
Flory has been following the issue closely, raising questions and continuing to push for answers from NASS and NASDA.
“The September anomaly in Nebraska was detected because there are three data points to reconcile – irrigated, non-irrigated and all. In other states, there is just one data point. That doesn’t tell us if the sample count was at planned levels,” Flory explained after the October report was released. “Because the ear counts are ‘raw data,’ counts for Iowa could have been based on one field or 500 fields – there’s no way to tell. That’s why this is so important. The Nebraska problem in September could be an isolated problem, but it is possible this is a broader problem, not a one-state problem.”
Flory says he does not question the methodology used in October and agrees the transition from survey-based estimates to actual harvest results is important.
“But only 15% of the Nebraska corn crop was harvested as of October 4. That means field observations from NASDA enumerators still likely carried significant weight in the October crop estimate from NASS,” Flory pointed out after the October report was released.
Is a Staffing Shortage to Blame?
The big question in Nebraska, according to Meyer, was why enumerators didn’t reach more irrigated fields in September. Irrigated and nonirrigated ground is “sprinkled amongst each other,” he says, so he wonders whether a geographic problem kept crews out of certain areas.
“I think that’s a legitimate question,” Meyer says. “I expect NASS will answer that.”
He doesn’t think a staffing shortage is the answer as to why NASDA didn’t sample more irrigated fields in September. Otherwise, he says, sampling issues would likely appear across a wider geography.
“If you were just short everywhere, then you wouldn’t see the skew of irrigated versus nonirrigated,” Meyer says. “So I think it has to be a geographic issue. I don’t know why.”
But other critics aren’t so sure staffing issues aren’t to blame. As one analyst told AgWeb, it’s possible NASDA didn’t have enough staff to collect the data in Nebraska.
The newly acknowledged processing error adds another piece to the questions surrounding September’s numbers. However, NASS has not said the error resulted from staffing or explained whether it was connected to the unusual irrigated-versus-nonirrigated sample mix.
Farmer Frustration Is Legitimate
With the October report’s market reaction, there’s no denying farmers are frustrated, especially considering this is the report the market will trade.
“The number that’s printed is the number that the algorithms trade. It clearly changes the trajectory of everything that we’ve thought for some time,” says Matt Bennett, of AgMarket.Net.
Meyer says farmer frustration is understandable, especially when one report can move the markets like Friday’s report did.
“Margins are poor. These people have their livelihoods on the line,” he says.
But he doesn’t think farmers deciding to pull back from answering surveys is the solution.
“I don’t think withdrawing your support and responses is the best answer either,” Meyer says.
For now, USDA’s October corn yield forecast remains at 181.2 bu. per acre, with production projected at more than 16 billion bushels. NASS’ correction of September data adds new context to the controversy, but it does not change the October numbers farmers and grain markets are watching.