WASHINGTON — The U.S. Department of Agriculture in its September Crop Production report forecast 2009 U.S. soybean production at 3,245 million bus, up 46 million bus, or 1%, from 3,199 million bus forecast in August, up 286 million bus, or 10%, from 2,959 million bus in 2008, and the largest on record.

Corn production in 2009 was forecast at 12,955 million bus, up 194 million bus, or 2%, from 12,761 million bus forecast in August, up 831 million bus, or 7%, from 12,101 million bus last year, and the second largest ever behind the 2007 crop.

The U.S.D.A. soybean forecast was slightly below the average of pre-report trade estimates while the corn forecast was slightly above the average of expectations.

The average soybean yield based on Sept. 1 conditions was forecast at 42.3 bus an acre, up 0.6 bus from August, up 2.7 bus from last year and the third highest on record if realized. Area for harvest was forecast at 76.8 million acres, unchanged from August, up slightly from June and up 3% from 2008.

Corn yield was forecast to average 161.9 bus an acre, up 2.4 bus from last month, up 8 bus from last year and the highest on record behind 2004 if realized, the U.S.D.A. said. Harvest area was forecast at 80 million acres, down slightly from June but up 2% from 2008.

The U.S.D.A. all wheat production estimate of 2,184 million bus was carried over from its August report. Wheat numbers will next be updated in the Sept. 30 U.S.D.A. Small Grains Summary.