Basis bids for soybeans and corn delivered by barge to U.S. Gulf Coast terminals firmed on Friday, reflecting rising costs for barge freight and slow grain sales by farmers, traders said. Also, the basis for both crops firmed at a few domestic processing sites this week, prompting Gulf shippers to pay up a bit to compete for fresh supplies. Freight costs ticked higher this week on Midwest rivers. Empty barges on the Mississippi River at Davenport, Iowa, were offered at 625% of tariff on Friday, up from 575% a day earlier. Offers also rose on the lower Ohio River but held steady on the Illinois River after firming earlier this week. CIF Gulf soybean barges loaded in July traded at 103 cents over Chicago Board of Trade August (SQ25) futures and were re-bid at 100 cents over futures, up 3 cents from Thursday’s bid. CIF August soybean barges also traded at 103 cents over futures and were re-bid at 102 cents over futures, up 6 cents from a day earlier. For corn, CIF Gulf barges loaded ...