Spot soyabean basis bids firmed in the US Midwest on Tuesday, reflecting strong demand from soya processors and a lack of country sales, dealers said.
Cash corn bids were steady to firm amid scattered light movement, dealers said.
The soya basis surged 20 cents in Toledo, Ohio, to 40 cents over the November soyabean futures contract.
"It's just following the processors. It's going to be erratic until harvest," an Ohio dealer said of soyabean prices.
Soya processor bids were up 5 to 15 cents in Indiana and Iowa, while Nebraska soya bids were up 2 to 4 cents.
Crushers have been aggressive in sourcing fresh supplies, inspired by strong margins and lingering concerns about whether old-crop soyabean stocks will last until the Midwest harvest begins. Unseasonably cool weather in the region this week threatened to slow crop development.
The early soyabean harvest was under way in the US Delta. USDA's weekly crop reports showed soyabeans were 3 percent harvested in Mississippi, while 12 percent of the Arkansas crop was turning color.
USDA said 73 percent of the US soyabean crop was rated in good to excellent condition, a surprise increase from last week's 70 percent. Traders had expected steady ratings.
CBOT soyabean futures were called to open 3 to 10 cents per bushel lower on the jump in crop ratings, traders said.
For corn, USDA said 76 percent of the crop was rated in good to excellent condition, unchanged from last week.
CBOT corn futures were called to open 1 to 2 cents lower on prospects for a huge US corn crop and calls for a sharp break in soyabeans, traders said.
Corn basis bids were steady to 2-1/2 cents firmer, supported by end-user demand. Tropical storms have slowed the early corn harvest in the US Southeast, prompting some buyers to source grain from other locations, a southern Ohio dealer said.
Cash basis bids for soft red winter wheat were steady to 2 cents firmer early on Tuesday, although Chicago wheat elevator bids declined late on Monday. Wheat movement was light.
CBOT wheat futures were called to open 1 to 2 cents lower on spillover expected from a setback in soyabeans. The sag was expected despite news early Tuesday that Egypt's GASC bought a cargo of 60,000 tonnes of US SRW wheat overnight along with an equal amount of French wheat.