Soybean selling should be due to slow, to judge by the date.

"Over the past four years, soybeans have bottomed during first week of October," Kim Rugel at Benson Quinn Commodities said.

Not that this necessarily means that the downward trend need necessarily be over.

"In two of those years, November futures expired higher while in other two the contract retested harvest lows again and expired near that harvest bottom."

But with the US harvest advancing, and nearer the end of the period when buyers have ready supplies to purchase off the combine, there is a seasonal trade of cashing in shorts at this time of year.

'Fund continues to liquidate'

As a further reason for caution over further selling, investors will have noted that Chicago's November lot closed just about its 100-day moving average in the last session.

Could that mark a point around which to build a rebound?

The contract on Wednesday dropped without difficulty through the 100-day line, below which it has not closed below for four months, and only giving funds cause to further liquidate positions.

"The soybean market likely remains under pressure as managed fund long continues to liquidate," Richard Feltes at RJ O'Brien said.

Estimate revision

Added cause to sell came from overnight estimates from broker FCStone that the US soybean crop would, in the US Department of Agriculture's next Wasde crop report, next week, be raised to 2.489m bushels.

That upgrade of 215m bushels reflected a yield pegged at 38.2 bushels per acre, 2.9 bushels per acre above the current USDA figure.

OK, not all observers are so upbeat, with Michael Cordonnier at Soybean and Corn Advisor sticking with his estimate of a 2.560bn-bushel crop and yield of 35.0 bushels per acre.

However, he did acknowledge that the risk was of a larger harvest.

'Cut the rationing'

The bottom line was, as Mike Mawdsley at Market 1 said, that "the soybean market is rethinking the size of this year's crop.

"With the higher stock number Friday, and potentially bigger production than expected, the carryout numbers may be larger than we have been thinking for a few weeks."

And by potentially a margin, according to calculations by RJ O'Brien's Mr Feltes.

"A 5 bushels-per-acre gain in the US soy yield to 40.3 bushels per acre would cut the 2012-13 US soy rationing from 487m bushels down to 100m bushels, and in so doing seriously undermine the case for $15.00+ a bushel soybeans," he said.

Watch out below

Technically, the next big mark for the November soybean is around the $15.17-a-bushel mark, the 50% retracement of this summer's rally, so an important point for followers of Fibonacci analysis, and also at the bottom of a chart gap dating back to June 29.

The contract fell through that with ease too to stand at $15.11 a bushel at 09:30 UK time (03:30 Chicago time), a decline of 1.3%, having touched a three-month low of $15.04 a bushel earlier.

Below that, the next support is the psychologically important $15.00-a-bushel mark, and beneath that…

"There was a gap made July 5 in the chart at $14.78-14.93 a bushel," Market 1's Mr Mawdsley said.

"If tested, that would be about a $3.00-a-bushel sell-off from the September 4 high of $17.89 a bushel."

'Upside should be limited'

Palm oil did its bit to try to support the oilseeds complex by claiming back some of its 8% losses of the last session.

Kuala Lumpur's December lot rebounded 3.0% from a three-year low for a benchmark contract to stand at 2,320 ringgit a tonne.

Not that everyone was so convinced by the recovery, which comes in the face of swelling Malaysian inventories, boosted by softish exports and a seasonal high in production.

The trend of output outpacing exports is "to continue through the fourth quarter, keeping [Malaysian] inventory levels above 2m tonnes, a psychological range seen as denoting an ample supply of crude palm oil in the market," Malaysia's Kenanga Investment Bank said.

"Hence, the crude palm oil price upside should be limited."

External weakness

However, grains suffered a further sell-down too, which it should be noted comes amid weak but not dire sentiment on external markets.

The likes of shares, Brent crude and London copper are lower, weakened by Australian data showing the country recorded its biggest trade deficit in August in three and a half years, result large down to lower volumes and prices of commodity sales.

Tokyo shares closed down 0.5%, while Brent crude was 0.7% lower, dropping below $111 a barrel.

The safe haven of the dollar was trading flat.

More corn?

But corn suffered a bit of a blow from FCStone estimates that next week's USDA Wasde report will show a US crop of 10.824bn bushels, on a yield of 123.9 bushels per acre.

While not a huge increase over the 10.727bn bushels production that the USDA is currently factoring in, many analysts have been expecting a further downgrade, and a yield of some 120 bushels per acre.

December corn stood 1.2% lower at $7.49 ½ a bushel.

'Import interest'

And with corn, on which bulls have staked hopes after lower-than-expected US inventory data on Friday, weakening, wheat for December dropped too, losing 1.5% to $8.58 ¾ a bushel.

"Wheat is retreating to the lower end of a 10-week trading range on slow export demand, improving US hard red winter wheat area moisture and lower-priced Black Sea/Australian wheat offers," Mr Feltes said.

Still, there is hope.

Luke Mathews said: "It appears the recent slide in prices may be sparking the interest of notable importers.

"Egypt's GASC is seeking at least 60,000 tonnes of milling wheat for December shipment while Japan is seeking to buy the most wheat in a month in their regular weekly tender."

The results later of the GASC tender stand to reveal just how competitive, or not, US wheat is.