Following widespread US planting delays this spring, traders have shifted their attention to production prospects for crops that got seeded.

Periodic light rains expected this week should benefit those crops.

"The rain is much needed now," said Don Roose, president of US Commodities.

As of 11:48 a.m. CDT (1648 GMT), the September corn contract on the Chicago Board of Trade was up 4-3/4 cents at $4.20-1/4 a bushel, after dipping to $4.13-1/4 earlier in the session, its lowest since May 24.

Corn prices tumbled on Friday when the US Department of Agriculture (USDA) pegged the US planted area well above market expectations but the market's focus is now shifting away from acres planted.

"Our attention is now focused on what the weather is going to be for the next couple weeks," Roose said.

Roose said the amount of rain, jet stream direction, and pressure systems are key things to watch for in the coming weeks as crops approach their key reproductive phase.

The USDA's weekly crop progress report issued after the market close on Monday left its rating for corn conditions unchanged from the prior week at 56pc.

At the same time last year, 76pc of the corn crop was rated good/excellent.

Analysts polled by Reuters had expected a slight improvement.

August soybeans were down 6-1/2 cents to $8.83-1/4 a bushel after ending sharply lower on Monday, anchored by ample supplies of the oilseed.

"There is more of a cushion with soybeans," said Roose. "There will be more of a surplus to fall back on."

The USDA left its crop condition rating for soybeans unchanged at 54pc good-to-excellent, versus a 71pc score a year ago.

Soybeans cast off support from Friday's lower-than-expected USDA acreage estimate and news of a trade truce between Washington and Beijing.

The market declined on concerns that Chinese demand for imported soy would waver due to hog herd losses caused by African swine fever, said Joe Vaclavik with Standard Grain.

CBOT September wheat was down 7-3/4 cents at $5.04 a bushel after earlier touching a new three-week low of $5.01-1/4 as favourable harvest weather in the US Plains weighed on the market.

The USDA said Monday that 30pc of the crop was gathered.

On the demand side, a tender on Tuesday by top wheat importer Egypt was expected to be dominated by cheaper Black Sea origins like Russian wheat, traders said.