Futures prices for grains and soybeans were mostly higher at the close Monday on the Chicago Board of Trade. ``There was a pretty good rally in soy oil that gave soybeans a good boost,'' said Joel Karlin, analyst with Research Department Inc. ``India bought into the palm oil market. African countries have shown some interest in vegetable oils, too.'' Corn was supported by a rumor that the Soviet Union might be interested in as much as 1 million tons, he said. Export news sent wheat prices higher, said Susan Leighty, grains analyst with Prudential-Bache Securities Inc. The U.S. Agriculture Department confirmed rumors that China had bid for 300,000 tons of the U.S. commodity, and rumors persisted that the Chinese would bid for 300,000 tons more. The Soviet Union was also said to be in the market for 500,000 tons of export bonus wheat, she said. Also firming wheat prices were weather reports calling for mild conditions in the next few days that might make the winter crop more vulnerable to a cold snap later, Mrs. Leighty said. At the close, wheat was 1 cent to 1{ cents higher, with the contract for March at $4.10} a bushel; corn was \ cent lower to { cent higher, with March at $2.37} a bushel; oats were { cent to 2{ cent lower, with March at $1.50}, and soybeans were 2 cents to 6{ cents higher, with January at $5.67 a bushel.