Wheat and soybeans took their turn under the cosh as the hope of another bout of fund buying spared corn from spearheading the latest bear mauling.
Disappointment at Tuesday's US crop estimates was, again, a big factor in weakening sentiment.
"The landscape has now changed," broker US Commodities said. "This is a bearish landscape."
But this wasn't the only downer, with the market awaiting too news from regulators on position limits in commodities, and whether index funds will be exempt.
"If they are not, all commodity markets could have a negative reaction as position limits for index funds would hinder their ability to buy as much as they can," Vic Lespinasse, at GrainAnalyst.com, said.
The thinking is that if index funds can't hold all the energy contracts they want, they will cut positions in other commodities to proportion – to avoid the risk of being, say, too corn heavy.
The latest thinking on Tuesday's data, which showed a collapse in US winter wheat plantings, has been to determine how many of the acres lost to winter wheat will be planted with corn, soybeans or wheat, come spring. Or not at all.
FC Stone estimated US corn acres rising 3m acres, soybean planting up by 3m, and wheat sowings falling 5m acres.
For soybeans, in particular, that looks bearish, given that many analysts had foreseen a small drop in sowings until the US Department of Agriculture dropped its winter wheat bombshell.
And if bears needed another reason to sell, South America continues to provide it, with prospects looking pretty sharp for Argentine and Brazilian crops.
"South America weather remains near ideal," US Commodities said noting that the region's soybean crop was "marching toward a record".
March soybeans stood 16 cents lower at $9.83 ¾ a bushel at 17:30 GMT, with the expiring January lot going out with a whimper, down 14.5 cents at $9.78 a bushel.
At least soybeans had decent weekly export sales behind them, of 754,000 tonnes, a luxury denied corn, which managed a weak 327,000 tonnes, and wheat, a feeble 182,000 tonnes.
Wheat for March stood 10 cents lower at $5.27 a bushel.
And corn had the extra headwind of a negative note from Goldman Sachs, the investment bank, which warned over the risk of a jump in plantings undermining prices.
Still, the crops, and in paricular corn, gained some support from the prospect of another bout of buying by index funds undertaking reweightings which necessitate buying of 2009 laggards such as grains to allow their position weightings to catch back up with those of the stars.
This might be the last round, with those following the Goldman Sachs index due to finish today.
Or they may finish tomorrow, given that they held off on Tuesday, when corn's fall by the Chicago exchange limit encouraged funds to wait and see if they could pick up corn any cheaper.
"Today will be the last day of index fund buying at the close with the possible exception of corn, where index fund buying could also be seen late tomorrow, since they didn't buy any on Tuesday, the day corn was locked limit down," Mr Lespinasse said.
Or it is possible they may engage in a double dose of buying later, playing a bit of catch up.
That said, some observers noted the huge volumes on Wednesday as a sign that funds had sated much of their appetite then.