By Ilan Brat

CHICAGO-Prices of wheat futures finished at a fresh low on Wednesday, as a stronger dollar and an improved outlook for output pressured prices. Corn prices declined and soybeans were mixed.

Wheat settled at the lowest closing price for a front-month contract since June 19.

The WSJ Dollar Index, a measure of the dollar against a basket of major currencies, rose, making U.S. supplies less affordable for foreign buyers and requiring U.S. prices to decrease to regain competitiveness. In addition to ample wheat stocks around the world, an improving outlook for the U.S. wheat crop is weighing on prices. Concern that heavy rains early in the summer could have damaged the U.S. wheat crop are easing with recent favorable weather, analysts said, brightening the outlook for output.

The September wheat contract on the Chicago Board of Trade closed 14 1/2 cents, or 2.8%, lower at $4.96 1/4 a bushel.

Corn futures also finished down, as traders reconsidered some of their estimates for corn production. Recent benign weather is spurring some traders to project that the U.S. Department of Agriculture, in its next report on the crop's estimated output, is unlikely to cut its yield estimates as much as many believe, a sign of projected better-than-expected production.

CBOT corn futures for September delivery fell 7 1/4 cents, or 1.9%, to $3.67 3/4 a bushel.

Soybean futures were mixed, as traders balanced strong demand for soybean meal with the pressure on corn and wheat, which can often drag down soybeans.

CBOT August soybeans added 8 1/4 cents, or 0.9%, to $9.83 a bushel. November soybeans shed 1 1/2 cents at $9.43 1/4 a bushel.

Write to Ilan Brat at ilan.brat@wsj.com

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