* USDA increases estimates for domestic wheat, corn, soy acres
* Soybean plantings fall short of analysts' estimates
* Traders watch for weather that could threaten crops (Adds USDA data, latest prices)
By Tom Polansek
CHICAGO, June 30 (Reuters) - U.S. wheat futures touched a six-year low on Thursday and corn hit an 11-week low after the U.S. Department of Agriculture said farmers had planted more of the grains than expected.
Soybean futures soared to their highest level in two weeks as plantings and crop inventories fell short of analysts' estimates.
The USDA, in an acreage report, said domestic all-wheat plantings totaled 50.816 million acres, topping forecasts for 49.869 million and the agency's March estimate of 49.559 million acres. Corn seedings were 94.148 million acres, above the high end of estimates from analysts who on average had expected acreage to fall from the government's March forecast of 93.601 million.
The robust plantings will likely add to an ample supply base of grains.
The USDA, in a separate quarterly stocks report, showed that corn inventories as of June 1 were the biggest since 1988 while soybean stocks for that period were the third-biggest ever.
"The surprise is in the corn acreage numbers," said Brian Hoops, analyst for Midwest Market Solutions. "I remember saying after the March report that we would not see that many corn acres."
December wheat rose 2 cents to $4.67-1/4 a bushel on the Chicago Board of Trade by 12:25 p.m. CDT. The most actively traded contract touched $4.36, its lowest price since June 2010.
December corn futures were down 13 cents to $3.70 a bushel. The most active contract touched $3.65-1/4, its lowest since April 13.
November soybean futures surged 44 cents to $11.56-1/2 a bushel.
The acreage report showed soybean plantings came in at a record 83.688 million acres, up from the government's March forecast of 82.236 million acres. Analysts, on average, had been expecting soybean plantings of 83.834 million acres.
"The bean number came pretty close to the average trade guess, but people out there had a 'fear number' that was 2.5 to 3 million acres higher than the average trade guess," said Jim Gerlach, president of A/C Trading. "When that fear wasn't realized, they considered it bullish."
The lower than expected soybean plantings estimate indicates that the market will be more susceptible to rallies driven by forecasts for threatening U.S. weather, traders said.
Corn and soybean prices have been swayed this month by such forecasts, against a backdrop of the risk that a La Nina weather pattern could trigger a dry summer in the U.S. Midwest. (Additional reporting by Colin Packham in Sydney and Gus Trompiz in Paris; editing by Jonathan Oatis and Tom Brown)