Argentina's wheat plantings, which fell to a century low last year, may plunge potentially by a further one-half thanks to government curbs which have accelerated a switch to other crops, Rosario Grain Exchange has said.

Such a shift would be likely to wipe Argentina - historically a bigger shipper of the grain than Russia and Ukraine put together - off the map of wheat exporters.

Farmers "aren't going to take a risk" on a crop which the government so tightly controls, with exports only permitted once domestic supplies have been assured, the exchange said in a weekly briefing.

The curbs, coupled with firm prices, only improve the attractions of soybeans, for which there is a 35% export tax but no restriction on volumes.

"The worst that could happen � and we're on that path � is that next [crop] year wheat plantings falls against and production is not enough to meet domestic demand," the report said.

North America's gain? 

The decline would continue a marked reversal for wheat in a country which, until two years ago, ranked not far behind Australia and the European Union in the exports league, with shipments of more than 10m tonnes.

Its exports for 2009-10 will come in at 2.5m tonnes, according to the US Department of Agriculture.

It would also force Brazil -which imports about 5m tonnes of the grain a year and has historically been Argentina's main wheat export market - to step up efforts to seek fresh supplies, a quest in which proximity is expected to give North America a head start.

'Exceptional yields'

The exchange added that, while corn sowings had also fallen in 2009-10, the harvest was on course to jump by more than one-third to 18.01m tonnes thanks to better growing conditions.

"Exceptional yields are compensating for a smaller corn area," the report said.

Drought sent the 2008-09 corn crop to 13.1m tonnes, on farm ministry estimates.

The exchange held its estimate for Argentina's soybean harvest at a record 50.8m tonnes, compared with the 31m tonnes a year ago, when the crop was also hurt by a lack of rain.

The report followed a 1.8m-tonne increase to 65.2m tones in industry hopes for the soybean crop in neighbouring Brazil.

The Brazilian Vegetable Oils Industry Association, or Abiove, also lifted by 1.3m tonnes to 27.1m tonnes its estimate for the country's soybean exports.