WASHINGTON (AP) _ Spring rains and summer flooding in the Midwest conspired with drought in the Southeast to cut this year's estimated corn crop to 6.96 billion bushels, among the smallest harvests in the past decade.

Only the drought-plagued years 1983 and 1988 saw lower production.

''We've seen this crop deteriorate from the first estimate that was taken back in August,'' Larry Rus, executive director of the National Corn Growers Association, noted after the Agriculture Department issued its monthly crop estimate Tuesday.

The department also lowered its estimates for the soybean, peanuts and wheat harvests.

Corn crops that got off to a late start because of the wet weather fell prey to September frosts in western and northern corn states.

Also, corn growers in Iowa, Minnesota and South Dakota destroyed late- maturing crops so they could qualify for government programs aimed at cutting flood-related financial losses.

Ohio, previously expecting a good harvest, suffered from a late-summer drought. North Carolina lost 50,000 acres in September because of lack of rain.

Georgia and South Carolina lost soybean acres, and a late flood in Missouri claimed 100,000 acres of beans there.

Tuesday's corn estimate was down 4 percent from one issued last month and 27 percent below the 1992 record of 9.48 billion bushels. A separate report from the department estimated the lower harvest drive up prices 5 cents a bushel, so they would range from $2.20 to $2.60.

''There should be some positive reaction in the market for those who do have a crop,'' said the corn growers association's Rus. ''It won't make up for the folks who have lost everything or have a reduced yield.''

Based on Oct. 1 surveys, the average corn yield nationally was estimated at 110.3 bushels per acre harvested, compared with the record 131.4 bushels last year and 113.1 bushels indicated last month.

Soybean production was estimated at 1.89 billion bushels, down 14 percent from last year's harvest of 2.20 billion bushels, which was the second highest on record. October's estimate, however, was just 1 percent below the September figure.

The soybean yield was forecast at 33.7 bushels an acre, just three-tenths of a bushel below the September estimate and 3.9 bushels below 1992.

Late plantings and slow maturity caused a slower wheat harvest, with the production forecast at 2.42 billion bushels. That compares with the September estimate of 2.49 billion bushels and the 2.46 billion bushels harvested last year.

Cotton production was put at 17.9 million bales, up 5 percent from last year's output of 16.22 million bales but 5 percent less than the September forecast.

Rice production was forecast at 165 million hundredweight, 2 percent below the Sept. 1 forecast and 8 percent below the 1992 total, but still possibly the third largest harvest on record.

Because of the drought, peanut production was forecast at 3.26 billion pounds, down 7 percent from the Sept. 1 forecast and down 24 percent from last year's crop, for possibly the smallest harvest since 1980.

All orange production was forecast at 10.3 million tons, down 7 percent from last season.