U.S. soybean and corn futures rose on Tuesday after weekly crop condition ratings declined, but mostly favourable weather in the Midwest crop belt kept a lid on rallies by backing expectations for large harvests, traders said.
Wheat firmed on a pick-up in global export business and declining estimates of the size of the harvest in Russia, the world's top wheat exporter.
Corn futures were only fractionally higher despite news that China booked its biggest single-day purchase on record of U.S. corn, buying 1.762 million tonnes of the grain.
The deal followed a 1.365 million-tonne corn sale to China announced on July 10.
Market reaction to the latest China sale, confirmed by the U.S. Department of Agriculture, was muted by plentiful old-crop supplies and prospects for big harvests this autumn.
"That's a pretty good number. But when all is said and done, even if USDA took their export forecast up 100 million bushels, we'd still have a large carry-out," said Terry Reilly, senior analyst with Futures International in Chicago.
In a weekly crop progress report late Monday, the USDA rated 69% of the U.S. corn crop as good to excellent, down from 71% last week.
It rated 68% of the U.S. soybean crop as good to excellent, also down from 71% previously. Analysts on average had expected smaller declines.
CBOT wheat futures firmed on short-covering and worries about global supplies. Sovecon, a Moscow-based consultancy, cut its forecast for Russia's 2020 wheat crop to 79.7 million tonnes, from 80.8 million previously, due to low yields in Russia's southern regions.