So if the last trading day of January did not bring selling, as month-ends often do by repute in agricultural commodities, does that mean that the start of February would not spark month-beginning buying?

The overarching concern in grain and oilseed markets remained South American weather rather than the calendar, and conditions which are bringing central Brazil strong rains, delaying harvest and interrupting crop flows to port, and southern Brazil and Argentina not enough moisture, threatening yields.

'Crop stress will continue'

In the last session, corn and soybean prices ebbed and flowed with every change in the thinking of unexpected thunderstorms in Argentina.

"Heavy rains fell over north west Cordoba into the western San Luis with amounts over 2.0 inches," with lesser precipitation over some other parts of central Argentina, (and none at all in many areas), weather service WxRisk.com said.

Did it change significantly crop prospects?

World Weather said that the moisture was "not enough for a lasting increase in soil moisture", adding that "crop stress will continue".

'Heat dome developing'

As for what lies ahead, WxRisk.com said that "weather models continue to show a heat dome developing over Paraguay and northern and central Argentina" which will last until "early next week and then begin to break down".

"As long as this heat dome is in place, Paraguay, all of central and northern Argentina and south eastern Brazil will see little significant rain, and that is why the weather models show no significant rains and most of these areas the next five days."

And even after that Rio Grande do Sul in southern Brazil "stays mostly dry, as does all of Argentina".

At broker Benson Quinn Commodities, Kim Rugel said: "Dry weather over the next 10-15 days for Argentina comes during key flowering and pod setting for central soybean producing regions.

"The market will be keenly attuned to any changes in outlook for next weekend."

China pledge

There was enough worry, anyway, to give bulls the benefit of the doubt, at least until the next runs of the weather models.

Also potentially moving markets later will be updated Informa Economics estimates on South American crop production.

And soybeans had extra support from demand too, after data on Thursday showed US weekly export sales of the oilseed rising 28% week on week to 1.25m tonnes, with a further 220,000 tonnes, bought by China, for 2013-14 revealed through the US Department of Agriculture's daily alerts system.

"Total sales over the past four weeks are running 89% above last year's pace, with most of the sales headed to China," Luke Mathews at Commonwealth Bank of Australia said.

And, sticking with China, Chen Xiwen, director of the Chinese Communist Party's top policy making body for rural affairs, said that the country would not impose further curbs on food imports this year.

"We should use both international and domestic markets to ensure farm product supplies and we should not go back to closing the gates," Mr Chen said, in comments closely watched for giving an insight into China's new government.

'Position is more precarious'

Soybeans, of which China is the top importer, rose 0.5% to $14.75 ¾ a bushel, for the Chicago March contract.

Signally, that took the lot just above its 100-day moving average, which it has not closed above for three months.

Corn, which China is seen becoming an increasingly important buyer, and which is now comfortably back above all its major moving averages, added 0.3% to $7.43 a bushel for Chicago's March contract.

Hopes for a recovery in US ethanol use from their lowest on record last week also helped.

"With ethanol margins improving slightly, the cash market for corn is also holding strong, supporting the spot contract," Joyce Liu at Phillip Futures said.

She added: "Both US and global stocks-to-use position is more precarious for corn than for soybeans, so adverse crop weather," as being seen in South America, "is likely to support corn more."

'Not driven by fresh demand'

It was wheat again which lagged.

Weekly US export sales, at 388,000 tonnes down one-third from the eight-week average, did not help.

"The $0.50-a-bushel, or+5%, rally in prices from January 9-22 was clearly not driven by fresh physical demand, raising concern about the likely longevity of the stronger prices," CBA's Luke Mathews said.

Furthermore, Chicago's March wheat lot has a relatively poor technical outlook remaining above only its 10- and 20-day moving averages.

The contract stood 0.2% higher at $7.81 ¼ a bushel, its premium over corn now well below $0.40 a bushel and counting.

China factor

Among softs, cotton, having proved the top gainer among crops, and indeed all major commodities, in January with a 10.5% rise, opened the new month with a more negative attitude.

New York's March lot fell 0.6% to 82.43 cents a pound.

US export sales of 137,000 running bales in the latest week, the lowest figure since October, have questioned whether consumers are willing to pay the higher futures prices.

"US futures are up more than 8 cents a pound over the past few weeks, but physical buyers have not chased the market higher," Mr Mathews said.

The export data signally included 11,100 bales in cancellations of Chinese orders, the first since July, and muffling any signal from Mr Chen about open import policy in China, the top buyer (producer and consumer) of the fibre.