The Agriculture Department yesterday reconfirmed that livestock feed will be in tight supply in the year to come, driving up meat prices.

This year's corn harvest is forecast at 6.46 billion bushels, down just slightly from last month's estimated crop production and down 17 percent from last year's record crops. The USDA adjusted its estimates for the soybean harvest up slightly to 1.77 billion bushels.

"All in all, what it means is a world a year from now when the 1981 crops are ready to be harvested in which there will be essentially no reserves of feedstuffs," said chief economist Howard Hjort. Hjort also announced that U.S. estimates of the Soviet grain crop have been revised down in keeping with recent gloomy predictions out of Soviet Union.

Not only do consumers face a year ahead with less meat at higher prices on the platter, they also face a year in which prices for peanut butter may skyrocket.

Peanut production is forecast at 2.3 billion pounds -- 8 percent lower than last month's estimate and 42 percent smaller than the 1979 crop. Prices for peanut butter -- often used as a lower-cost protein substitute when meat prices go up -- could rise by as much as 50 percent to 60 percent.

Retail food prices are expected to rise between 10 percent and 15 percent in 1981 compared with an increase of about 9 percent expected this year, most of it for meat.

Cotton production is estimated at 11.2 million bales, up 1 percent from October's forecast but 22 percent less than last year's record crop. Overall oilseed production, including soybeans and peanuts, is forecast at 55.4 million metric tons, down 23 percent from last year.

Much of the decrease in corn and other crop production reflected the devastation from drought and hot weather. USDA officials reiterated yesterday that the drought had more impact on farm prices than the embargo on grain sales to the Soviet Union.