Grain and soybean futures prices were sharply down Monday on the Chicago Board of Trade, as a result of increased harvest pressures and declines on the precious metal and energy markets. Wheat futures prices fell to levels from two weeks ago amid doubts the Soviet Union does not plan to buy subsidized wheat flour from the government, along with professional selling by major companies and near-ideal harvest conditions, analysts said. ``There's a very weak export outlook to buy grains,'' said Walter Spilka, an analyst with Smith Barney, Harris Upham and Co. in New York. ``You're moving grains into positions to be sold and you don't have any ready buyers, so that's going to push prices lower.'' Soybean futures pushed toward double-digit losses as major corporations sold off their interest. Near-ideal weather conditions in areas where the crop is grown also added pessimism the entire harvest would be sold, Spilka said. Corn followed soybeans and wheat amid the same fears. At the close, wheat futures were 7} cents to 3\ cents lower with the contract for delivery in December at $2.70a bushel ; corn was 5 cents to 1{ cents lower with December at $2.23 a bushel; oats were 1{ cents lower to { cent higher with December at $1.19{ a bushel; soybeans were 11} cents to 5 cents lower with November at $6.06\ a bushel.