Argentine soybean prices fell over the past week on expectations that South America is on track for record crops this season.

Spot soybeans sold for 1,780 Argentine pesos per ton ($356) at the Rosario Grain Exchange Thursday, down from ARS1,815 a week ago.

Better weather conditions in both Argentina and Brazil auger well for the developing crops and weighed on global prices this week, the Rosario Exchange said. Traders also are expecting the U.S. Department of Agriculture to project larger U.S. supplies in Friday's crop reports.

Brazil and Argentina are the world's no. 2 and no. 3 soybean exporters behind the U.S. and wet weather and high prices stoked record planting this year.

Argentina's soybean planting is 91% done with the crop developing well, according to the Buenos Aires Exchange.

The U.S. Department of Agriculture expects Argentina to grow a record 55 million metric tons of soybeans, up from the previous record of 52.7 million tons set during the 2009-10 season.

Meanwhile, March, April and May new-crop corn contracts sold for $195 a ton at the Rosario Exchange, up from $190 a week earlier.

Corn prices got a boost on expectations for lower corn production in the U.S., the Rosario exchange said.

Argentina's corn planting is 88.5% done, according to the Buenos Aires exchange.

Argentina, the world's no. 3 corn exporter behind the U.S. and Brazil, is expecting a corn crop of between 26 million and 27 million metric tons this season, topping the previous corn record of 24 million tons during the 2010-11 season, according to the corn chamber Maizar.

Spot wheat sold for $230 a ton at the Rosario exchange Thursday, up from $220 a week earlier. Worries over the upcoming U.S. wheat crop helped support prices, the Rosario exchange said.

Write to Shane Romig at shane.romig@dowjones.com

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(END) Dow Jones Newswires

January 10, 2013 15:25 ET (20:25 GMT)