One big factor separated trading on Friday from that in the previous session.

And that was the revelation by Apple of results below market expectations.

The technology giant, the world's largest company by market capitalisation, after the close of trading in New York last night unveiled earnings of \$8.67 a share for its fiscal fourth quarter, below average estimates of \$8.75 a share.

The miss, while not massive, was poorly received by investors, following disappointments from other groups such as Google too during the US earnings season.

And, with uncertainty over US growth data due later too, financial markets got off to a negative start.

Downward trend

Shares fell 1.4% in Tokyo, and 1.7% in Seoul and Shanghai, the safe haven of the dollar edged higher, while, among commodities, Brent crude lost 0.5% to drop below \$108 a barrel.

In the agriculture space, the trend was generally downward too, with Chicago crops extending their losses of the last session, although this time it was grains which were more resolute.

Soybeans for November lost 0.5% to \$15.56 ¾ a bushel as of 09:10 UK time (03:10 Chicago time), continuing to come under pressure from soft US weekly export sales data released on Thursday.

Sales slowdown?

OK, at 522,000 tonnes the soybean export sales data were hardly abysmal.

And the US Department of Agriculture also separately revealed a sale of 120,000 tonnes of soybeans to an unknown importer, which the market presumed to be China, after a series of rumours of the country in the market for further purchases.

But the statistics were below expectations, and do appear to indicate a slightly slower, if solid, trend this month.

Sure sales are running well ahead of the rate needed to meet USDA projection of 2.165bn bushels for the full 2012-13, reaching nearly 920m bushels so far.

However, they are expected to tail-off in the second half of the season, as South American supplies come on line.

Better data

By contrast, wheat export sales were, at 572,000, considered healthy, and potentially a signal that international values were at last rising to make US supplies more competitive.

"With the Black Sea out of business, the US is a major player in the near term," Darrell Holaday at Country Futures said.

The data were especially promising when "one considers that there is very little movement of soft wheat", Brian Henry at Benson Quinn Commodities said, terming sales of hard red spring and hard red winter wheat "good".

"The pace of weekly wheat export sales remain well behind the pace of prior years, but Thursday's figure did exceed the 525,200 tonnes amount required each week to meet the USDA export expectation."

'Story has shelf life'

Not that this is the only factor in play in wheat.

There are continuing fears over Argentine and Australian crops heading towards harvest.

And a changing of indexing policy has prompted a fund to plan to switch some of its wheat exposure to Kansas (home of hard red winter wheat trading) from Chicago (where soft red winter wheat is traded).

Some 23,000 Kansas cargoes will be bought, at the expense of 56,000 lots in Chicago around the start of 2013.

"This story has shelf life and it isn't a very long one," Mr Henry said.

Also on the negative side, in Chicago, was the fall in the last session of the December lot back below its 50-day moving average, a negative signal for funds.

The contract added 0.3% to \$8.75 ¼ a bushel on Friday to remain well below the line.

(This session, unlike the last, it did better than its Kansas peer, down 0.25 at \$9.15 a bushel, but which remains above its 50-day moving average.)

'Certainly some nervousness'

And signals for funds do need to be watching amid talk that something broader in the way of selling is afoot.

"There is certainly some nervousness as there is more talk about funds liquidating long positions in some ag commodities after the run up this year to balance their year-end portfolios," Country Futures' Mr Holaday said.

"That is a normal move and does not seem out of the ordinary," he added, but of course is hardly positive for the commodities sector.

The CRB commodities index in the last session hit its lowest since early August, before staging some recovery.

Corn import problems?

Also on the rumour front, there is talk of Brazilian corn destined for the US east coast being sold on, at a profit, for shipment to Europe.

The talk is that phyto-sanitary certification proving tricky to obtain for entry to the US, although why it should be any easier for Europe which has higher barriers to GM varieties, albeit not for a Syngenta variety given clearance earlier this month....

That the EU needs corn is not such a surprise, although the bloc "is not expected to be overly active over the final two months of the year after having bought 12-15 cargoes of Brazilian corn in the past seven-to-10 days and are now said to be covered through the New Year", Mr Henry said.

However, if Brazilian corn does have a knack of running into trouble getting into the US, that could put further upward pressure on the domestic cash market as the feed groups which have turned to South America for cheaper supplies are forced to rebuy in the domestic market.

'Almost non-existent'

Certainly, the US cash corn market is already firm enough, supported by a reluctance by growers to sell anything bar low-quality supplies, even if futures are feeling softness from the relatively high US prices which have prompted buyers to turn to South America.

In fact, US export sales were 142,300 tonnes in the latest week, below trade expectations, and continuing a trend of poor shipments.

"Exports are almost non-existent at the moment," Mike Mawdsley at Market 1 said.

December corn eased, but by 0.3% to \$7.40 a bushel, given some support by weak.

Investors should also note that Friday brings the close of November options, which for corn are grouped around \$7.50 a bushel, and may provide some gravitational pull to that level.

For soybeans, the main grouping is at a strike price of \$16.00 a bushel, which seems less likely to come into play.

Cotton falls

Among soft commodities, cotton renewed a downward trend, falling 0.4% to 72.43 cents a pound in New York for December delivery.

US export sales data for the fibre came in at 47,700 running bales, well below the pace of the previous week, and indicating that last week's spike in prices indeed slowed demand.

There is, after all, enough supply about.

Cotlook raised its forecasts for the world cotton surplus in 2012-13 by 16%, citing better hopes for Chinese and Indian crops.