Wheat rediscovered its mojo on Tuesday, with a little help from Russia, helping limit declines in other Chicago crops.

There was plenty of temptation for investors to keep removing premium from corn and soybeans.

Overnight data showed an increasing proportion of the corn crop rated "excellent". The combined figure, with that rated "good", was 72%, not far below the record high of 77% set six years ago (which achieved then-record high yields too).

The relative figure in soybeans was a lower, but still very respectable, 67%.

'Weather looks favourable'

And there is little sign of anything which would get crops in difficulty, for now.

"Overall weather looks favourable to corn and soybeans," Darrell Holaday at Country Futures said.

US Commodities added that weather forecasts were "non-threatening into August 10".

Furthermore, external markets performed poorly, with a fall in US consumer confidence nearly wiping out on share markets the boost given by upbeat results from Deutsche Bank and UBS.

Oil, often a leader for crops used as biofuels, slipped 1.8%. (It has lost some of that influence over corn, to judge by the turn to negative of bioethanol margins).

(Another) Russia downgrade 

But wheat helped corn for September end a modest 1.5 cents lower at $3.62 ¾ a bushel, with August soybean ending a mere 0.25 cents lower at $9.98 a bushel.

New crop November soybeans ended 0.5 cents down at $9.65 ½ a bushel.

Wheat's spur was goings on in Russia, where SovEcon, the analysis group which has appeared to have its finger best on the parched and fading pulse of the country's crops, once again downgrading its grain harvest forecast, saying it could now come in below 70m tonnes.

Last year's crop, remember, was 97m tonnes, with the result topping 108m tonnes in 2008.

To export, or not? 

And then there was the issue of what the Kremlin was going to do about it. Buyers have been increasingly afraid that the country will, as it has done in the past, close its doors to exports to protect domestic supplies.

Russia is, after all, attempting to beef up its livestock industry, a drive which hardly looks best served by allowing feed grain to leave the country.

These fears were crystallised in a Renaissance Capital note suggesting that there was a "high chance" of the introduction of some restrictions – high export tariffs or somesuch.

The note helped wheat recover early losses to go back above $6 a bushel in Chicago at one point, before closing at $5.95 a bushel, up 0.9% on the day.

Paris wheat for November set a new high-since-September-2008 of E184.25 a tonne before retreating to end at E180.75 a tonne, up 1.8% on the day, while in London, November wheat finished up 1.7% at £133.20 a tonne.

Europe, with its relative geographical proximity to Russia, stands to be the first in line to benefit as an exporter should the price-competitive Black Sea grain giant give up on shipments.

Sugar reveral

Retreats were the order of the day in sugar too, with New York's benchmark October raw sugar lot getting above 19 cents a pound for the first time since mid-March only to reverse to 18.41 cents a pound, down 1.1% on the day.

The decline was blamed largely on forecasts for Brazil's coast which did not look as dire as had been forecast. Wet weather delays the loading of the sugar crop which buyers are baying for to replenish depleted stocks. (Especially, it seems, Islamic countries, which face imminently the festival period of Ramadan.)

Not that all investors are convinced by sugar's late decline, with some pointing to a surge in volumes in options, and mostly in calls, as a sign of residual buying interest.

And Commerzbank said that, for Brazilian sugar supplies to keep up, the sweetener needed to reassert its attractions with ethanol, an alternative (and marginally more popular) destination for cane.

While the proportion of cane processed into sugar had risen by 2 points to 46% in late June, thanks to the stronger sugar market, "in order for the portion to remain that high, the sugar price should increase more, because the price for ethanol has also risen recently".

White sugar, at least, held on to positive territory, edging up $0.50 to $566.60 a tonne in London.