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Improved weather in northern hemisphere pushes down prices

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Russia pushes back on Black Sea grains deal

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U.S. Agriculture Department reports flash corn sale to China

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MEXICO CITY, April 13 (Reuters) - Chicago grains futures reversed earlier gains to close lower on Thursday, as weather improved and despite Russia saying there would likely be no extension of the wartime grains corridor deal, analysts said.

Soybeans lost ground from their earlier rally as weather in the northern hemisphere looked clearer.

"U.S. weather is pretty darn good everywhere but the southern plains, where the dryness is epic," Charlie Sernatinger of Marex Capital said in a note to clients.

"There was a ton of corn getting planted to close the week, with two tons of field work happening, and even a few bean fields in the eastern belt were getting seeded," he added.

Wheat went lower, too, despite new threats from Russia that there would be

no extension

of the U.N.-brokered Black Sea grain deal beyond May 18, unless the West removed a series of obstacles to the export of Russian grain and fertilizers.

Corn fell, in part due to lower export demand, despite a U.S. Agriculture Department report of 327,000 tonnes of corn sold to China.

The most-active soybean contract on the Chicago Board of Trade (CBOT) settled down 3-1/4 cents at $15.01 per bushel, after climbing earlier to its highest since April 5 at $15.22-1/4.

CBOT corn closed 3-3/4 cents lower at $6.52-1/4 per bushel, after touching a one-week high earlier. CBOT wheat settled down 12-1/2 cents at $6.67 per bushel.

The USDA said export sales of wheat totalled 203,500 tonnes, corn export sales totalled 527,700 tonnes and soybean export sales totalled 430,500 tonnes in the week ended April 6.

Brazilian farmers will produce a record 153.6 million tonnes of soybeans this season, according to a report by statistics agency Conab, an increase of 2.2 million tonnes compared to a March forecast as harvesting draws to a close in the world's biggest exporter of the oilseed. (Reporting by Cassandra Garrison in Mexico City, Gus Trompiz in Paris and Naveen Thukral in Singapore; Editing by Sonia Cheema, Kirsten Donovan, Krishna Chandra Eluri and Diane Craft)