Perhaps predictably, grains chose to end their rally just as shares were refinding their feet.

Stocks enjoyed a firm day, notably on Wall Street where the S&P 500 index reached its highest in five years, helped by optimism over the US after data on Thursday showed US weekly initial jobless claims tumbling and housing starts soaring.

And many commodities managed headway too, with the CRB index adding 0.7%, and among ags, New York arabica coffee gaining 1.6% to 154.50 cents a pound for March delivery, attributed in part to technical buying

"Today we initially saw light small spec support but certainly as we tested higher it did bring in fresh technical buying and this encouraged day traders in too," if against pressure from producer selling, Sucden Financial said.

Data from consultancy Safras & Mercado showing 60% of Brazil's coffee crop sold received a mixed response – being well below the 76% figure a year ago, so signalling more beans yet to sell, but ahead of some of the more downbeat expectations too.

Strong exports 

However, grains and oilseeds rediscovered their knack for moving the opposite way to other markets – even corn, which ended its longest winning streak since June.

The problem was not so much a lack of fresh bullish news, with weekly US export sales data, for instance, deemed "impressive" by US Commodities and "supportive" by rival broker Country Futures.

The US sold 393,000 tonnes of corn, the second highest number of 2012-13 and more than twice some expectations, and more than 570,000 tonnes of wheat, old crop and new combined.

"These are not seen as great numbers in a normal year, but strong numbers given the recent export activity," Country Futures' Darrell Holaday said.

'Bullish price risk'

For soybeans, the total reached nearly 1.8m tonnes, including 2013 crop, a number termed "massive" by RJ O'Brien and the highest in eight months.

Mr Holaday said that while Chinese buyers accounted for more than 1m tonnes of that, the market had been aware of much of this through earlier US Department of Agriculture announcements, meaning "the impressive number was the amount bought by other countries".

After all, the world is not far from seeing Brazilian export supplies come onstream, with harvest already begun – although some rain delays, and logistical hiccups, could put a spanner in the works.

"In the very short term we feel there is some bullish price risk in the soybean complex as we go through the transition from US to Brazil export dominance," Macquarie noted, flagging that "the timing of the early-harvested Brazilian soy will be critical".

"The forecast of heavy precipitation in the coming weeks risks delays to harvest and thus export potential. Any supply potential lost from Brazil in February will have to be sourced from the US."

Lost competitiveness?

However, the support from the export data was muted by the fact that it related in the week to last Thursday – the day before the USDA data which reignited bullish sentiment in corn and wheat particularly.

Price rises since raise questions over whether the strong exports will continue.

"US wheat was competitive in the world trade until the recent sharp rally," Paul Georgy at broker Allendale said.

Nor was there any ideas of the recent South American dryness worsening, and requiring the injection of more risk premium.

"A couple of weeks of dry weather in this region does not put us on the brink of the poor production experienced last growing season," Benson Quinn Commodities said.

'Borderline alarming'

OK, the US weather picture did take a turn for the worse with a National Oceanic and Atmospheric Administration forecast showing that above-average temperatures look likely this summer for the western Corn Belt and the US Plains – still suffering from the last drought.

"The updated NOAA US summer temp forecast will reinforce concerns over the upcoming 2013 US weather pattern," RJ O'Brien's Richard Feltes said, terming the outlook "borderline alarming".

But long-term weather outlooks are notoriously unreliable. And on a more immediate horizon, Mr Feltes also noted that the "cold blast across US early next week still coming buy looking less severe than yesterday", important when some US wheat is said to be lacking a snow blanket.

'More risk premium'

Even a downgrade by Strategie Grains to expectations for the European Union wheat crop, following on from an industry caution on Wednesday over Russia's winter grains, and against lingering concerns over US winter wheat, failed to spark much reaction.

Nor did an International Grains Council reduction in its estimate for world corn stocks, to 113m tonnes, 3m tonnes below the USDA figure.

But have such numbers already been factored in?

There was some expectation that price falls were only temporary, with Mr Fletes saying he suspected that ag markets would "add more risk premium" ahead of the weekend.

'Less shame in getting caught short'

However, investors looking for more reassurance from technical signals received little, with corn dropping back right to its 50-day moving average, and soybeans trading up to their 200-day moving average, at $14.46 ¼ a bushel, only to fall back again.

"Despite the supportive export data released this morning, I'd find less shame in getting caught short from these levels than getting caught long," Benson Quinn Commodities said, adding that  "producers should be rewarding this rally" by selling into it.

Corn actually led the retreat in Chicago, falling 0.9% to $7.24 ½ a bushel for March, its first decline in nine sessions, and further reinflating its discount to wheat, which for March dropped 0.5% to $7.81 ¼ a bushel.

March soybeans eased 0.4% to $14.30 ¼ a bushel.

Fibre favoured

Among soft commodities, cotton also performed respectably, adding 0.6% to 77.78 cents a pound, and earlier touching an eight-month high of 78.18 cents a pound.

Strong weekly US export sales of 339,000 running bales further improved sentiment stirred by expectations of a large drop in US sowings with the fibre this year, as low prices deter growers.

Macquarie forecast a "near-20%" drop in acres.