Market bears, who have already raked their claws aplenty through agricultural commodities this month, saved a large swipe for the last day.
They gained extra fortification from a broadly negative macro-market environment, with renewed fears over the eurozone outweighing better-than-expected results from the US from a Chicago factory survey, and a University of Michigan consumer sentiment report.
But knocking grain futures down was anyway as easy as falling out of bed after the US Department of Agriculture discovered an extra 200m bushels of
Grain prices at close on Friday
Chicago wheat: $6.09 ¼ a bushel, -6.9%
Chicago corn: $5.92 ½ a bushel, -6.3%
Chicago soybns: $11.79 a bushel, -4.2%
Paris wheat: E183.50 a tonne, -3.8%
London wheat: £150.65 a tonne, -3.7%
Prices for near-term contracts
"Today's USDA grain stocks report was bearish for the entire grains and oilseeds complex," Rabobank said.
"The USDA delivered a substantial blow to grain market bulls today by providing significantly higher corn stock estimates than expected."
At GrainAnalyst, trader Matthew Pierce was more colourful.
"The overall report was ragingly bearish. The USDA simply shut bulls down today," he said.
Corn for December spent most, if not quite all, the live trading session down the exchange limit of $0.40 a bushel, equivalent to 6.3%. Indeed, the lot ended there, at $5.92 ½ a bushel, the lowest finish since December.
And that sent other grains down too, including
Paris wheat for November ended down 3.8% at E183.50 a tonne, the lowest for a spot contract since July last year in the early days of the grains rally.
London wheat for November closed 3.7% lower at an 11-month low of £150.65 a tonne.
Still, just when it may have looked that it was all over for bulls, Minneapolis hard red spring wheat provided some hope, reviving back into positive territory not long before the end of play before dipping back to end down 0.4% at $8.92 ¼ a bushel.
USDA crop stocks estimates, change on last, (and on market forecast)
Corn: 1.128bn bushels, +208m bushels, (+166m bushels)
Soybeans: 215m bushels, -10m bushels, (-10m bushels)
Wheat: 2.15bn bushels, n/a, (+104m bushels)
US stocks data as of September 1
And analysts made some positive noises too, with Mr Pierce noting hope for prices rebounding, especially factoring in dry South American conditions.
"At the last four quarter ends things have bottomed before making new highs. I feel there is no reason things cannot bounce significantly once this flushout is over," he said.
At Country Futures, Darrell Holaday said: "This may be the bad news that puts in a seasonal bottom in price."
The weakness spilled over into other agricultural markets too, with cotton for December ending down 2.0% at 100.19 cents a pound.
The USDA data was "raining on a lot of parades today", Louisiana-based cotton analyst Mike Stevens said.
"Yesterdays excellent performance in cotton now seems for naught, dropping our market back into the range either side of 100 cents a pound we had been in the previous six sessions."