It's a difficult concept to remember sometimes, but US row crop yields don't always meet forecasts.

"Numerous reports indicate yields… have been very disappointing to growers. A colder and wetter than average August are largely being assigned as the culprit."

The crop in question was cotton, rather than corn or soybeans, for which US harvest results continue to come in largely ahead of forecasts.

And the comment, from Ron Lee at Georgia-based McCleskey Cotton, was aimed at reports on crops "from Louisiana north to the Mississippi Delta".

'China reserve stocking'

Not that all has been disappointing for US cotton production prospects at all, with Mr Lee also, for instance, flagging forecasts earlier in the week of the key area of west Texas receiving "more than 6 inches of rain this week with well below temperatures, both of which would certainly be unwanted".

However, the "cold and rain did arrive, but in less quantity than expected, and damage apparently is minimal at best".

Indeed, the consensus still remains of a large US crop.

Still, on the more bullish side for prices, Mr Lee also flagged continued market assessments that the "possibility/probability of a sooner-than-expected reserve restocking [in China] is pretty good.

"Everyone that I talk to expects China's demand to be stronger than expected during this marketing year," a factor Mr Lee saw as preventing a collapse in prices unless the US harvest "ends up being 22m bales or bigger".

On call

In fact, 67.00 cents a pound "seems to be the number that will hold this market as far as December futures go", he added.

And New York cotton futures for December remained comfortably above that level in early deals, adding 0.2% to 69.08 cents a pound.

Ecom flagged another balancing act going on in the cotton market, between mills, which have 29,900 contracts worth of cotton "on call" against the December contract, ie with the price to be fixed against the lot, while merchants have 17,500 contracts to sell on call.

However, that represents a drop of 1,200 contracts in the mill total week on week, which Ecom said gave it "more hope that as the mills and producers on call positions become more of a 1:1 ratio then the market will have the ability to grind lower without as much support".

Data later

For grains, US production prospects will also come into debate later when the US Department of Agriculture unveils updated estimates for output of summer-harvested grains, notably wheat, as well as data on domestic inventories of major crops as of the start of this month.

The wheat report is expected to cut the official estimate of the all-wheat crop by 21m bushels to 1.718bn bushels, reflecting drought damage to spring wheat in the northern Plains.

That said, there is considerable uncertainty over both major moving parts in this calculation – ie how badly yields were affected, and how much of the crop never made it to harvest.

Indeed, the range of forecasts for the all-wheat figure is large, from 1.66bn-1.761bn bushels, with some commentators expecting an increase to the production estimate.

'Production could surprise'

"Wheat production could surprise" in today's report, Benson Quinn Commodities said, noting that "trade is leaning lower" in its spring wheat harvest estimate, but with the forecasts too of a larger crop.

Chicago wheat futures eased 0.4% to $4.53 a bushel for December as of 09:20 UK time (03:20 Chicago time), undermined too by ideas of much-needed rain for the eastern Australian crop.

Sydney east coast wheat futures for January fell 1.8% to Aus$280.00 a tonne overnight, taking to 5.6% their retreat from Tuesday's peak.

That said, they gained 10.7% for the month.

Biggest since 1988

Back in Chicago, corn and soybean futureseased too, as often is seen as happening in fact at month ends, when funds are viewed as often withdrawing cash, but fuelled this time by continued talk too of largely better-than-expected US harvest yields.

But the focus is on the USDA stocks data later, expected to show US inventories as of September 1 at 2.353bn bushels, the highest since 1988, with the soybean number seen at 338m bushels.

With quarterly stocks data having a record of causing large market moves, this has stolen attention for now from the rains seen boosting Brazilian sowing prospects, and the debate over the Environmental Protection Agency rethinks on US biofuel mandates.

Corn for December eased by 0.4% to $3.51 a bushel, while November soybean futures eased 0.3% to $9.56 ¼ a bushel.