Tuesday might have been expected to be weak in Chicago.

The second day of the week, by repute, reverses a strong trend seen on the first, which this time saw upwards as the default direction.

But in fact there was something of a Turnaround Tuesday on many markets, with investors appearing to succumb to the temptation of profit-taking appearing.

Tokyo's Nikkei share index snapped an eight-day winning stream, to close down 0.3%, with Shanghai stocks shedding 1.0%, and Hong Kong shares 0.9%.

Many commodities started easier too, with Brent crude shedding 0.3%, and London copper showing small losses.

'Started to green up'

The cautious sentiment abroad did little to help the likes of wheat, especially after data overnight from US farm officials showed precipitation continuing to revive the health of US winter wheat crops, after a dismal start thanks to drought since sowing in the autumn.

Although the Texas crop stayed stable at 18% in "good" or "excellent" health, the Oklahoma crop improved to 20% in those ratings bands, up four points week on week.

The Kansas crop was rated 27% good or excellent, up three points week on week.

"The Kansas wheat crop has started to green up and operators are top-dressing fields where conditions permit," farm officials in Kansas, America's top wheat-producing state, said.

Luke Mathews at Commonwealth Bank of Australia said while ratings were "still low in outright terms, further improvements are likely this month", given the precipitation improvements.

'Extra wheat going into feed'

This took some of the heat out of ideas that substitution of wheat for higher-priced corn might go some way to tightening the US wheat balance sheet.

"There continues to be talk of additional wheat being moved into the feed ration with rumours of significant soft red winter wheat sales over Chicago into western Kansas tying into last week's news that Bunge lowered their rate from Chicago into feed lots," Brian Henry at broker Benson Quinn Commodities said.

"The availability of soft red winter wheat and in some cases hard red winter wheat has resulted in higher levels of wheat being funnelled into the feed ration," he said, adding that while "the values definitely work, but there are limits to how much can be fed".

There are doubts too about the degree to which US ethanol plants, said to be seeking wheat instead of corn, can substitute grains.

Chicago wheat for May shed 0.5% to $6.96 ¾ a bushel as of 09:30 UK time (04:30 Chicago time).

Corn vs soybeans

And that only invited further substitution, with Chicago corn itself fending off most of the Turnaround Tuesday pressure to stand 0.25 cents lower at $7.11 a bushel for May delivery.

Besides the boost to sentiment from Friday's US Department of Agriculture 100m-bushel upgrade to its estimate for US feed use of the grain, more than offsetting a decline in the export figure, corn was supported by ideas that China has been stocking up, with orders since February of new crop reportedly reaching 600,000 tonnes.

It that was one sign that values of new crop corn, at least, might have gone a little far on the downside for now, another is the comparison with new crop soybeans – a key determinant of which crop farmers prefer in spring sowings, which in turn has a big impact on final crop size.

"The corn-to-soybean ratio has been slowly trending higher since the beginning of the year which could mean soybeans get more acres than early estimates were calling for," broker EHedger said.

While December corn eased 0.3% to $5.52 ½ a bushel, November soybeans dropped 0.8% to $12.60 ½ a bushel, eroding the soybean:corn ratio back to 2.28.

Export doubts

The decline in new crop soybeans was reflected in the rest of the complex, with May soybeans falling 0.9% to $14.65 ¾ a bushel, amid concerns over a long-feared drop-off in US exports, thanks to the seasonal rise in Brazilian supplies.

Monday's weekly US export data, as measured by cargo inspections, at some 17m bushels were, while well on target to meet USDA forecasts for the full 2012-13, well down week on week.

Furthermore, "the USDA has not confirmed new sales under daily reporting for several days which has disappointed the market, with setbacks in market seen at 08:00 over the past several trading sessions", Kim Rugel at Benson Quinn Commodities said.

Sure, Brazil's logistical hold-ups still look extensive for now, driving importers to purchase from the US instead, even at higher prices.

'May cause prices to plunge'

At Phillip Futures, Joyce Liu said: "For as long as the Brazilian port delays last, we see more potential for upside in the old-crop soybean contracts.

"But once the logistical issues are cleared, the sudden influx of Brazilian soybeans may cause Chicago soybean prices to plunge."

As an extra caution, the soy prices in China, where strong margins have been seen as allowing them to pay up for US supplies, took a dive.

Dalian soybeans for September dropped 0.9% to 4,724 yuan a tonne, with September soyoil down 1.1% at 8,154 yuan a tonne, and September soymeal tumbling 2.0% to 3,343 yuan a tonne.

Chicago soyoil for May shed 0.8% at 50.05 cents a pound and May soymeal dropped 0.9% to $434.10 a short ton.

In Kuala Lumpur, palm oil, the rival vegetable oil to soyoil, dropped 1.7% to 2,408 ringgit a tonne.

Technical indicator

Ms Liu was more upbeat over prospects for raw sugar futures, flagging a positive chart sign even from the price declines over the last two years.

A line connecting the descending price lows since then shows a far weaker slope than a line connecting the descending price highs, coming to a point around the end of the year

"The descending wedge pattern is a strong bullish signal if and when sugar prices break out of it," she said.

To get really technical: "With prices now trading at the upper channel of the narrow range and MACD (moving average convergence/divergence) line crossing above both the signal line and zero line, there is a strong case for a sustained bull rally in sugar prices."

'Susceptible to short-covering gains'

This would marry too with ideas that sugar prices need to buck up their act if mills in Brazil, the top sugar producer and exporter, are not to switch to turning cane into ethanol instead, given changes in taxation and blending rates in the offing.

Still, New York raw sugar for May stood unchanged at 18.82 cents a pound.

CBA's Luke Mathews added that "the massive speculative short position means prices remain susceptible to further short-covering gains".