Soybeans were again the pick of the bunch in early deals on Tuesday, as the dollar turned tailwind and investors reconsidered just how real the threat of the South American harvest really is.

The greenback helped all dollar-denominated farm commodities by weakening a touch, and so making exports more competitive, as traders took profits ahead of the US Federal Reserve's latest meeting to decide on interest rates.

 Furthermore, fears for China's economy, and Greece's debt, disappeared from the radar screen, at least temporarily.

Indeed, Shanghai shares were 0.5% higher at 07:40 GMT, with soybeans and soyoil higher on China's Dalian commodities exchange too.

Logistical issues 

Soybeans, and its products, followed suit in Chicago, helped by growing concerns over how effective Brazil is proving in getting its record crop to ports, and so the world market.

While Brazil is really beefing up its act as an agricultural powerhouse, its infrastructure has yet to match up to its farming ambitions, leaving farm trucks in Mato Grosso state to queue 25 miles at times to deliver to railheads.

Indeed, five state governors were due on March 15 to announce a new rail project for Lucas do Rio Verde, a farming-based town in the north of the state.

"With the low dollar and expensive freight rates, the new railroad is mandatory to keep central Mato Grosso viable as a production centre," Brazil farm consultant Kory Melby said.

"I hope they can survive until the railroad arrives."

Meanwhile in Argentina, which is actually at the start of its corn harvest, there are rumours of a potential strike in the port of Rosario.

Corn rally ahead? 

Such talk has helped remove, for now, the perceived threat to US soybeans from China, the biggest buyer of the oilseed, switching its import favour to South America.

May soybeans stood 7 cents higher at $9.37 a bushel.

And this gave some support to the grains, encouraging investors to take an optimistic view of the technical factors which look a good hope of support.

As Mike Mawdsley at broker Market 1 pointed out, corn on Monday had a so-called "inside day" – moving within the boundaries of its range the trading day before – with its lows of last week appearing to represent something of a floor.

"Now can we rally to the moving averages? We certainly think so," Mr Mawdsley said, signalling a rise to at least $3.72 a bushel for the May contract, its nine-day moving average.

The lot stood 1.25 cents higher at $3.64 ½ a bushel at 07:40 GMT.

Red River flooding 

On the fundamental, supply and demand, side, hope seems to have faded somewhat for sufficient Midwest rain to dent significantly US corn plantings. But there is some thought of flooding around the Red River in northern America and southern Canada, thanks largely to snowmelt.

"The Red is predicted to crest at 37-39 feet in Fargo, North Dakota this weekend just below the record 40.84 last year," Kevin Kjorsvik at Benson Quinn Commodities said, adding that the potential for flooding in a big spring wheat area had supported Minneapolis prices.

Chicago wheat for May stood 0.75 cents higher at $4.80 a bushel, with its Minneapolis equivalent up 1 cent at $5.08 ¼ a bushel.

Palm rebuilds discount 

Sure, that gain was slight. But it was more than palm oil could boast as it shed 19 ringgit to 2,556 ringgit a tonne, a one-month low.

The 6% decline from last week's highs, despite decent export data from cargo surveyors, represents in part a loss of momentum after the trade data and conference talk which had boosted prices.

However, it also looks like palm oil is regaining some of its historic discount to soyoil, which some observers had predicted could turn into a premium.