U.S. grain and soybean futures jumped Tuesday as weakness in the dollar and increasing concerns about crop conditions boosted prices.

Corn for December delivery, the most actively traded contract, rose 19 3/4 cents, or 3%, to $6.80 1/4 a bushel at the Chicago Board of Trade. Soybeans for November delivery gained 14 1/4 cents, or 1.1%, to $13.49 3/4, while soft red winter wheat for September delivery rose 9 3/4 cents, or 1.4%, to $7.05 1/2 a bushel.

The soft dollar lifted the markets as it makes U.S. grains more attractive to foreign buyers. The support was a turnaround from last week, when strength in the dollar and concerns about a global economic slowdown knocked grain prices sharply lower.

Concerns about threats to the developing corn and soybean crops helped boost prices, as traders worried that output could fall short of expectations. The U.S. Department of Agriculture, in a weekly crop report, reduced its condition ratings for some states. The agency increased its good-to-excellent and poor-to-very-poor ratings for the corn crop by one percentage point each from last week.

"People figured out it's an extremely variable crop out there," said Jack Scoville, vice president of Price Futures Group, a brokerage in Chicago.

Traders are paying close attention to crop conditions after excessive rains and flooding stalled field work this spring, preventing farmers from planting all the acres they had intended. Corn futures have pulled back nearly 12% since reaching a record high near $8 a bushel earlier this month on concerns that demand would outpace available supplies.

Fears about the risk for hot, dry summer weather to hurt output carry prices higher, traders said. Yet, warmer temperatures expected next week should be beneficial to developing crops, as long as temperatures don't climb too high for too long, said John Dee, president of Global Weather Monitoring, a private weather firm.

"Short term, it's probably a very good thing," he said about the warm-up.

Asian demand for grain has perked up following last week's selloff, as well. Buyers are taking advantage of lower prices to make purchases. Japan, the world's top buyer of corn, booked 300,000 metric tons of feed-grade corn for shipment from July to September, while the Korea Corn Processing Industry Association snapped up 55,000 metric tons.

Other markets

December soyoil settled up 1% at 57.95 cents a pound, while July soymeal rose 0.5% to $351.70 a short ton. September rice advanced 0.07% to $14.85 per hundredweight. September oats edged up 1% to $3.61 1/2 a bushel, and August ethanol rose 2.2% to $2.698 a gallon.

At the Kansas City Board of Trade, hard red winter wheat for September delivery closed up 0.2% at $8.21 1/2 a bushel. Hard red spring wheat for September delivery gained 0.7% to $8.85 1/4 a bushel at MGEX in Minneapolis.