Despite one of the worst batterings on record by drought and heat, U.S. farmers still are going to outproduce the Soviet Union, which is having one of its best harvest years in history.

Overall, total U.S. grain production is now estimated at 212 million metric tons, down 24 percent from 1987.The Agriculture Department issued that downward revision Tuesday. But in a related report, it released figures on total Soviet grain production that show the United States is still far ahead.

USDA said total Soviet grain production this year is forecast at a bumper yield of 215 million tons. But that figure includes peas, beans, buckwheat, rice and other miscellaneous commodities in addition to wheat, barley, sorghum, corn and rye.

Many of the secondary crops are not included in the U.S. grain total. Thus, if only soybeans are added - projected at 44.9 million metric tons this year - the drought-shriveled U.S. harvest still towers over the bumper Soviet yield.

A metric ton is about 2,205 pounds and is equal to 36.7 bushels of wheat or soybeans, or 39.4 bushels of corn.

The special U.S. crop report showed that the 1988 corn harvest may produce 5.2 billion bushels this year, 29 percent less than expected a few months ago and 26 percent below last year's bumper harvest.