Grain and soybean futures closed mostly lower Tuesday on the Chicago Board of Trade amid slack export demand and forecasts for showers and cooler temperatures in the Corn Belt later this week. Corn futures prices fell nearly 10 cents a bushel, the permitted daily limit. The corn market was the leader in a session that featured relatively light trading and wide price swings in the soybean pit. Soybean futures, which are limited to moves of 30 cents a bushel, have recently provided direction to the grain markets. But soybeans lost traders Tuesday to the lower-risk corn pit, said Steve Freed, a grain analyst in Chicago with Dean Witter Reynolds Inc. Despite a record-melting heat wave that threatens further damage to the drought-stressed soybean crop, Freed said speculators shied away from the soybean market when prices for near-month delivery approached $9 a bushel Tuesday morning. Meteorologists predicted cooler temperatures would begin moving into the Midwest on Thursday. The forecasts, plus a lack of substantial export business, left the markets with little bullish news. ``It's still a bullish market, but it's a market that has trouble finding itself on days like today,'' Freed said. At the close, wheat was 1{ cents to 3} cents lower with the contract for delivery in September at $3.90{ a bushel; corn was 4} cents to 9} cents lower with September at $2.87{ a bushel; oats were 4{ cents to 9} cents lower with September at $2.78{ a bushel; soybeans were 21 cents lower to 20 cents higher with August at $8.66 a bushel.