UPDATE 1 — US corn rating seen steady, harvest 13% done; soy rating likely down
(Updates with USDA data) By Karl Plume CHICAGO, Sept 21 (Reuters) — U.S. corn and soybean condition ratings held steady at three-year lows over the past week, as harvesting of both crops advanced modestly despite widespread rains in parts of the Midwest, according to a weekly U.S. Department of Agriculture report relea