You can't keep a bad thing up.
There were some suspicions that the recovery in grain and soybean prices seen in the last session would prove short-lived.
Sure, row crops managed to put a string of decent fundamentals together, in terms of a deteriorated weather forecast, decent soy export demand and strong cash markets, to counter the elephant in the trading room of mega US crops seen ahead.
But a big part of the rising prices was also down to the uncertainty ahead of a key US Department of Agriculture crop report on Monday encouraging investors to cover short positions, and it was unclear how big the appetite for that was.
Darrell Holaday at Country Futures said: "Yesterday there was some commercial buying that surfaced to protect against bullish USDA numbers on Monday.
"But that buying did not seem very deep."
Rain for Iowa?
"I suspect the soy market will trim weekly gains late session," Richard Feltes at Chicago-based broker RJ O'Brien said, flagging in fact the large South American crops that will compete with the US for export market share in 2013-14, and likely 2014-15 too.
Furthermore, the concerns over dryness in the western Corn Belt, over which some traders have been angsting, took a back seat with forecast from the US National Weather Service of rains for South Dakota and, importantly, Iowa over the next three days, particularly over the weekend.
Not that all meteorologists were convinced.
"The problem is that no model data is showing rain like that, so I am not sure why they are making that forecast," David Tolleris at WxRisk.com said.
But it was enough to reduce buying pressure on that score.
The case for covering shorts in corn ahead of the Wasde was, anyway, relatively weak, if history is a guide, given that the USDA August corn production has beaten trade expectations in seven of the last nine years.
And ideas of strong yields received a further boost from results of crops tours, with Lanworth using field evidence to nudge higher to 14.06bn bushels its forecast for the US corn harvest, and by 10m bushels to 3.32bn bushels its estimate of the soybean crop.
Weather service MDA, on the fourth day of its Midwest tour, reported a better day for Iowa, lifting the state average yield estimate to 201.9 bushels per acre, up from 154.2 bushels per acre found last year, and even better prospects for south western Minnesota, at 214.3 bushels per acre.
Yields "continued to exceed expectations and remained remarkably consistent", MDA said.
Furthermore, there is some feeling that ideas that Tyson Foods' ban on cattle fattened by Zilmax would boost corn production may be misplaced.
Corn for December closed down 1.4% at $4.53 ¼ a bushel, the contract's lowest close since October 2010.
'Basis posted further gains'
Soybeans did fare better, as might be expected given that in 11 out of the last 12 years, the USDA's August Wasde production forecast has fallen short of investor forecasts.
Furthermore, as Mr Feltes noted, "soy basis posted further gains yesterday on light farm sales and firming soymeal spreads."
And there are the background concerns that a late sowing season will mean late development and a late harvest, leaving crops susceptible to the early onset of winter, with soybeans particularly vulnerable to low temperatures.
"Many fear an early frost could greatly reduce production," CHS Hedging said.
Soybeans for November eased 0.2% to $11.82 ¼ a bushel.
Corn's weakness dragged on fellow grain wheat too, which was also little helped by an upgrade in the official forecast for the French crop, the European Union's biggest, by 200,000 tonnes to 36.1m tonnes, following some improved results as harvest moves north.
Elsewhere in the EU, Romania's farm ministry pegged the domestic harvest at an eight-year of 7.3m tonnes, meaning strong supplies to direct at export markets.
The Black Sea producer is a renowned price competitor, and indeed has won half the 1m tonnes or so of wheat that Egypt, the top importer, has ordered so far in 2013-14.
In the US itself, US Commodities said that forecasts over the next 10 days indicate that "harvest delays should be minimal in the northern plains wheat areas", helping speed the bringing in of the spring wheat harvest.
Chicago wheat for September shed 1.2% to $6.33 ½ a bushel, with the December lot losing 1.0% to $6.47 ¼ a bushel.
Paris wheat for November actually ended unchanged at E183.00 a tonne, albeit only after posting a contract low of E182.00 a tonne, while malting barley for November gained 0.6% to E204.00 a tonne, ending a soft week on a resilient note.
Soft commodities made a better fist of following the broader commodities sector in posting gains, with the CRB index adding 0.7%.
That said, cocoa struggled a bit against profit-taking, after posting multi-month highs in the last session on both sides of the Atlantic, and taking gains in London to more than 5% this month.
London cocoa for December eased 0.3% to $1,643 a tonne, although New York's December lot edged $1 higher to $2,480 a tonne, the highest finish of 2013.
"There has been only little rainfall in recent days in the cocoa growing areas of West Africa, and the forecast for the next two weeks is no better," Commerzbank noted.
"The lack of moisture could have a negative impact on the main harvest, which is due to begin in October."
With West Africa accounting for about two-thirds of world cocoa output, "the cocoa price remains well-supported", the bank said.
However, arabica coffee for September added 0.7% to 122.90 cents a pound, helped by the Brazilian support programme unveiled this week, and by spillover support from London robusta beans, which for November gained 2.1% to end at $1,949 a tonne.
The rise in robusta followed data showing a sharp fall in stocks held for delivery against London futures, to 83,770 tonnes as of Tuesday, from 98,250 tonnes on July 22.
And raw sugar added 1.0% to 16.98 cents a pound, helped by data from cane industry group Unica showing sugar production falling 14.8%, year on year, in the second half of July.