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Corn spot basis bids were up 1-3 cents per bushel at ethanol plants in Iowa and Illinois while bids eased by 2 cents along the Illinois River.
Soybean bids were 11 cents per bushel higher at a terminal along the Mississippi River in Iowa and mostly flat elsewhere.
Chicago Board of Trade corn and soybean futures were little-changed as traders squared positions in advance of the USDA data.
Analysts polled by Reuters expected the government to narrowly increase its estimate for US corn production and average crop yields and slightly reduce those estimates for the soybean crop.