Google managed to reverse early optimism on many markets. But for Chicago, matters of the virtual world came a distant second to considerations about actual shortfalls in crop supplies.

The feeling that a seasonal low has been put in to grain and oilseed prices, as Agrimoney.com highlighted earlier, only gained momentum, gradually, over the day.

After all, crops typically lose downward pressure when harvest ends, and with it the once-a-year spike in supplies.

Then attention turns to cash markets, which are being supported by a reluctance by growers to sell at levels well below summer highs.

'Lower hedge pressure'

"The cash market is driving this market higher," Darrell Holaday at Country Futures said.

"With harvest winding down - basically finished - basis levels are reflecting the tighter supplies and have moved to stronger levels throughout the major areas," with corn in Illinois apparently going for $0.60-a-bushel above December futures.

Benson Quinn Commodities said: "Corn and soybean harvest is nearing completion easing producer hedge pressure on markets."

US Commodities said: "The cash markets are firming as harvest winds down. Corn is supported by the lack of farmer selling and the firmer basis levels."

Even in the cotton market, Georgia-based cotton broker Keith Brown said that "corn and soybeans look they have put in their harvest lows".

'Dangerous day'

And that meant a rethink for bears who have had harvest pressure on their side the last month or more, driving down soybeans nearly $3 a bushel from summer highs at one point this week, with corn down $1 a bushel.

"This is a key day for soybeans," US Commodities noted early on, saying that, technically, futures were "at reversal price levels and oversold".

"This is a dangerous day for the shorts if the market pushes higher."

Which it did, closing up 2.3% at $15.45 ½ a bushel for the November contract.

'Much drier than desired'

Sure, there were hurdles for the oilseed, such as a weekly US export sales figure which, at 523,000 tonnes, fell short of forecasts of at least 650,000 tonnes.

However, on the price positive side, Country Futures' Darrell Holaday noted that more northerly parts of Brazil "remain much drier than desired", with the sowings window wide open, even if rains further south appear to be boding well for the crop – in driving farmers from corn.

And there is still talk of plenty of Chinese interest in US soybeans, even if this was not so evident in the weekly data.

Furthermore, the buying improved the crop's chart picture, driving the November lot back above its 10-day moving average, for instance, only reducing further  the pressure to sell which has marked so many recent sessions.

'Talk of Chinese interest'

Corn's export sales were disappointing too, at 166,000 tonnes, below forecasts for at least 200,000 tonnes, if reaching a level more than 10-times those of the previous week.

Still, there are ideas China might buy here too, contrary to waning market figures for the country's imports, following an apparently decent harvest.

"There is talk of Chinese interest in buying corn and wheat to replenish reserves," Mr Holaday said.

"It does not matter where they buy it. If the Chinese buy a substantial amount of corn or wheat, it is bullish," with some 300,000 tonnes of wheat already purchased from Canada, reports this week said.

US vs Brazil

Furthermore, US corn is beginning to look more competitive, or at least less uncompetitive, on export markets, with South American prices rising as supplies erode.

"The corn basis levels in Brazil have rallied $0.40 a bushel from the lows and has helped narrow the discount to the US," US Commodities said.

"The US remains the most expensive world corn. The spread however is narrowing."

And after all, the poor pace of Argentine corn sowings, and some losses in southern Brazil too, are raising fears over the early-2013 harvest.

As an extra fillip to prices, Strategie Grains reduced further its forecast for the European Union corn harvest.

Corn for December added 1.9% to $7.60 ¾ a bushel.

Southern hemisphere setbacks

That was some help for wheat, which lacked quite the rallying point for a rally, as it were, that the row crops did in the seasonal low theme.

Some long-running factors are in wheat's favour, including persistent doubts over the Australian crop, and with the Buenos Aires grains exchange restating a forecast for the Argentine harvest of 10.1m tonnes, well below the USDA estimate.

Furthermore, US export sales were, at 410,000 tonnes, a little above expectations, even if as Benson Quinn Commodities pointed out, the "accumulative pace remains behind last year".

Wheat for December added 1.4% to $8.68 ½ a bushel.

Chicago vs Paris

That was enough to regain a little ground from Paris wheat for November, which gained 1.3% to E259.75 a tonne, after in the last session posting a fresh high in its spread against the Chicago benchmark lot.

"This is coming with French wheat meeting the lion's share of recent tenders," Rory Deverell at FCStone said.

Still, London wheat did better, gaining 1.5% to £201.40 a tonne for November delivery, after Agrimoney.com revealed that UK rains were adding insult to injury by hampering significantly sowings for the 2013 crop, after slashing the quality and quantity of the newly-finished harvest.

Coffee sell-off

Among soft commodities, New York December cotton ended a hugely volatile session – extending from 1.7% gains to limit down – by closing down just 0.2% at 77.72 cents a pound.

The extent of the late recovery bodes well for trading in the next session, Keith Brown at broker Keith Brown & Co said.

But New York arabica coffee for December achieved less on the rebound front, ending down 1.8% at 158.60 cents a pound, the lowest finish for the contract in nearly four months.

"After a good week of knocking on the door at the 160/159-cents-a-pound support level, prices on have finally broken through, and after all that winding up, with some force too," Sucden Financial said.

Below 160 cents a pound "stops were triggered", meaning automatic sell orders, "and speculators began to short the market", before some roaster buying steadied the market.