CHICAGO: Spot basis bids for corn and soybeans were mostly steady across the US Midwest on Wednesday as support from rain delays to the harvest was offset by pressure from forecasts for historically large stockpiles of the crops, grains merchants said.

Farmers have sold only small amounts of their harvests in recent weeks, delivering mostly supplies they sold earlier this year at levels much higher than current cash prices.

The slow pace of sales as well as heavy rains this week that kept farmers out of the fields resulted in a few grain buyers boosting bids. The soybean basis gained 4 cents per bushel at a closely monitored processor in Decatur, Illinois, and 2 cents along the Mississippi River.

Corn futures are hovering near a three-year low while soybeans touched a 1-1/2 year low this week, chilling any selling interest from farmers even as they continued to gather a record corn crop and the fourth-largest soy crop in history.

Activity in the cash grains market could remain subdued until after the release at midday on Friday of the US Agriculture Department's monthly supply and demand report. The government is expected to triple its estimate of corn supplies for the coming year, analysts said.