GRAINS-Corn slumps to one-week low as U.S. supplies hit marketReuters Staff3 MIN READ * U.S. harvest advances, set to flood market * Wheat firms on Black Sea dry weather concerns * Soybeans edge higher By Colin Packham SYDNEY, Oct 4 (Reuters) – U.S. corn fell to a one-week lowon Wednesday as North America’s harvest began to fill the marketwith supply. U.S. wheat edged higher to extend two-day gains to 1 percentas dry weather across the Black Sea stoked fears of lowerproduction, while soybeans moved higher. The most active corn futures on the Chicago Board of Trade were down 0.2 percent to $3.48-3/4 a bushel by 0209 GMT,near the session low of $3.48-1/2 a bushel – the weakest sinceSept. 27. Corn closed down 0.6 percent in the previous session. “Despite earlier concerns, the season has shaped up prettywell and the harvest is advancing at a steady rate,” said PhinZiebell, agribusiness economist at National Australia Bank. The U.S. Department of Agriculture on Monday said the cornharvest was 17 percent complete, and it rated 63 percent of thecrop as good-to-excellent, an improvement from 61 percent a weekearlier.