By Ilan Brat

CHICAGO--Wheat futures finished at a fresh low as a strengthened dollar and an improved outlook for output pressured prices.

Corn declined and soybeans were mixed.

Wheat prices 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. Concerns 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.

Wheat was affected by a "strong undertow of ample world supplies," said Rich Feltes, vice president of research at R.J. O'Brien in Chicago.

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.

Money managers that had bet corn prices would rise as weather damaged the crop have been selling their positions amid improved weather, adding to pressure on corn contracts, Mr. Feltes said.

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

Subscribe to WSJ: http://online.wsj.com?mod=djnwires