Chicago corn lost more of its hard-won territory as fears for a freeze in the US Midwest evaporated, overpowering helpful data from both the US and China.
Washington reported US export sales of corn at 966,000 tonnes, better than investors had expected.
The second potential bullish factor was an estimate from Yue Guojun, assistant president of Cofco, that China's corn crop would come in at only 148m tonnes this year, more than 15m tonnes below official forecasts.
Not that the estimates from Cofco, China's biggest grain trader and corn processor, were totally unexpected.
"Considering the last month's dry weather, [official] estimates seem optimistic and local analysts [forecast] a drop of 12m to 20m tonnes this year," French analysis group Agritel said.
"Early harvest in the northern regions of the country will give a better idea of Chinese potential."
Indeed, traders remained fixated on the chances of a US freeze, which appeared to be dwindling, and with them, the risk of damage to what appears a huge American corn crop.
Corn for December stood 3.1% lower at $3.26 a bushel at 17:20 GMT. The fall left the contract 6.3% off its high on Tuesday, when frost fears sent the lot limit up at one stage.
Soybeans did better, losing 2.75 cents to $9.47 ¾ a bushel. But then they had seen less reaction to the frost threat.
Wheat was 6.25 cents lower at $4.61 a bushel, as weak corn and a Brazilian decision to check US cargos for vomitoxin offset potentially bullish data from Informa Economics.
Among softs, coffee was one of the better places to be, hitting a five-week high in New York, although technical buying rather than fundamental reasons were said by traders to be behind the increase.
New York arabicas for December stood 1.5% higher at 136.20 cents a pound, with London's robusta bean contract for December delivery ending $12 higher at $1,524 a tonne.
Profit taking was blamed for a slide in sugar, which ended $5.60 lower at$586.00 a tonne in London for December delivery, with New York's October raw sugar contract standing down 0.14 cents at 22.63 cents a pound.