Brazil, which is expected to overtake the US in soybean exports, has already beaten it in corn shipments, underlining the South American country's growth as an agricultural superpower.

The 3.4m tonnes of corn which Brazil shipped in January extended a shipment spree which saw the group last year trounce its previous record for a calendar year, of 10.9m tonnes set in 2007.

Exports were supported by a record safrinha, or second, crop planted as a follow-on in fields cleared by the soybean harvest, and which enjoyed unusually benign growing conditions last year.

"Brazil is blowing the doors off on corn exports," Richard Feltes at RJ O'Brien, the Chicago-based broker, said.

'Has already happened'

Indeed, it appears that the US Department of Agriculture's 21.5m-tonne estimate for Brazilian corn shipments in Brazil's 2011-12 crop year, which ends this month, "is understated by 2m-3m tonnes", Mr Feltes said.

"It looks like Brazil for first time will displace US as the world's number-one corn exporter."

"In fact, it has already happened," Mr Feltes said – if on the basis of comparing 2011-12 data for Brazil for the 2012-13 season for the US, whose exports are being depressed by last year's dismal harvest.

That is not the stretch in accounting that it may appear, given that Brazilian season and US crop years, which start in September for corn, overlap by six months.

'This does matter'

Brazil's catch-up is "somewhat down to luck", Mr Feltes acknowledged, flagging the coincidence of an unusually strong safrinha crop with such a poor one in the US, which recorded its lowest corn yield in 17 years.

However, its improving trade muscle does "highlight an important shift, where the likes of Brazil are becoming major corn exporters," challenging America's historic dominance.

"They are far more aggressive in pricing corn for export than the US."

This is shifting custom from the US which may not return, even when the country's yields resume their historic improving trend and harvests improve – at a time when demand growth from ethanol plants has levelled off.

"Once buyers have got used to the particular qualities and specifications of corn from another country, they may stick with it," Mr Feltes said.

"In the long-term, this does matter."

Farming superpower

The dynamic also places Brazil at the pinnacle of world supplies in yet another agricultural commodity, after gaining top rank in coffee, orange juice and sugar exports.

The country is also the top chicken meat exporter, and was the top beef shipper before being overtaken by India last year, and a major source of cotton supplies.

And it is poised to overtake the US in soybean shipments too – once the current harvest begins in earnest.

Indeed, Brazil's corn shipments could yet stay strong, if rains continue to delay the soybean harvest and hamper deliveries to ports.

"Soybeans are going to take priority when they get to port. But until then, Brazil can keep shipping corn," Michael Cordonnier, at Soybean and Corn Advisor, said.