Some say they have seen a head and shoulders.

Darrell Holaday, at broker Country Futures, said that "a bear flag formation became very evident".

Whatever, either pattern in the soybean chart was a negative sign which added to traders' enthusiasm to sell the oilseed on Thursday.

Remembering that funds have a net long position in the oilseed so large "it looks not manageable", Brian Henry at Benson Quinn Commodities said.

"The corn long position is probably manageable, but very, very large," and the wheat net long the most easy for the market to digest on a liquidation wave.

'Not good news'

And there were more than chart signals behind investors' appetite for sales, especially in soybeans, which for Chicago's November contract tumbled to their lowest close in more than a month.

External markets hardly helped, with risk assets depressed by HSBC data showing Chinese manufacturing activity still slowing, if at a slightly lower pace than last month.

Darrell Holaday at Country Futures said: "Seven straight months of negative manufacturing data out of China. That is not good news for the soybean complex," with the country the top importer of the oilseed.

Shanghai stocks fell to their lowest since February 2009, and eurozone data hardly improved the mood, showing private sector activity dropping at its fastest pace in three years.

The safe haven of the dollar added 0.4% against a basket of currencies, an indicator of a cautious mood, besides lowering the affordability of dollar-denominated exports, such as many commodities.

'Yields are better than expected'

But there were fundamental negatives for soybeans too, helping them capture notable trading volumes compared with corn and wheat, as liquidation took hold, with funds selling an estimated 16,000 contracts.

The over-riding depressant is of forecast-beating US yield results (albeit ahead of low forecasts, given the summer drought), at a time when harvest pressure is weighing anyway on values, as a once-a-year spike in supplies comes onstream.

"There is little doubt that the feeling in the industry is that soybean yields are better than expected," Mr Holaday said.

Richard Feltes at RJ O'Brien said that it appears currently that "the trade is worried more about the large fund long, harvest hedge pressure and better-than-expected soy yields than it is about running out of beans next spring".

Where are the Chinese?

And the demand hopes behind the last session's rally dried up too.

OK, US weekly soybean export sales were solid, at 712,000 tonnes, towards the upper end of market expectations.

But that was for last week. The dearth of official confirmation of Chinese buying since, despite plenty of talk of purchases on the break in prices earlier this week, stoked many a doubt.

Rumours of purchases of 2-10 cargoes "have been circulating for several days and we have yet to see any announcements on the daily sales report", Paul Georgy at broker Allendale said.

Soybeans for November dropped 3.0% to $16.18 ¾ a bushel.

Mixed demand picture

That made corn look relatively upbeat, in dropping only 1.4% to $7.46 a bushel.

And this despite another week of dismal US export sales data, of a little under 70,000 tonnes.

"Corn sales need to average 430,000 tonnes to meet the USDA goal" for 2012-13, US Commodities said.

"Export corn remains non-competitive. South American corn is well under US export values."

Still, at least there are signs of hope in domestic demand, with ethanol production "now above breakeven", meaning "ethanol plants are coming back online after being idled earlier in the summer", the broker said.

"Egg sets and broiler placements are not showing liquidation. Basis levels on corn are firming, up $0.15 a bushel across the Corn Belt in the last week."

'Somewhat supportive'

Still, it was left to wheat again to show the best performance among Chicago,s big three crops, closing down a modest 0.2% at $8.79 ½ a bushel for December delivery.

Besides the lack of a fund overhang, US weekly export sales, at 488,000 tonnes, topped expectations.

And the weather outlook was "somewhat supportive", Mr Feltes noted, showing "lighter showers forecast across Western Australia, and prospects for continued dryness for the north west quadrant of the US hard red winter wheat belt", signalling some challenge to ideas of a rise in US sowings of the grain.

Furthermore, Russian wheat seems to be losing export competitiveness too, at least against some non-US origins.

In Europe, Paris wheat showed small gains, adding 0.1% to E261.25 a tonne, while its London peer eased 0.6% to £205.10 a tonne, despite a downgrade by consultants Adas in their estimate of the UK wheat crop, potentially to a 20-year low.

'Triggered sell stops'

Among soft commodities, cotton suffered, as might be expected as an industrial commodity in an atmosphere of enhanced economic worries

New York's December lot dropped 1.6% to 75.22 cents a pound.

And New York arabica coffee for December dropped by 3.3% to 161.60 cents per pound, in part on a technical move, after the lot's short-covering rebound earlier in the week failed again to find any echoes.

"After what initially looked like a pullback from the short covering rally seen in previous weeks, now looks like a failure to move any higher as prices break the 171.70-cents-a-pound support level," Sucden Financial said.

"This move triggered sell stops and the market continued to fall."

Sugar data

However, raw sugar rose, boosted by talk of rain slowing the revival in the cane crush in Brazil's key Centre South region.

Furthermore, trade association Unica put dampeners on Czarnikow forecasts of lower prices yet by cutting its forecast for Centre South sugar output in 2012-13 to 32.7m tonnes.

Raw sugar for October added 1.3% to 19.21 cents a pound.