Shipping by barge using barge rates on the Mississippi River system can fluctuate in response to changing demand conditions. The benchmark used to measure rates is a tariff rate established for each location on each river. Barge rates are then traded as a percentage of this tariff.
Base barge rate tariff link.
The weekly Grain Transportation Report
For example, the tariff rate from Minneapolis, MN is $6.19 per short ton. This is the equivalent of $0.186 per bushel for soybeans and wheat and $0.173 cents per bushel for corn. If the freight rate for a barge loaded in Minneapolis, MN bound for the gulf export market is trading for 200% of the tariff rate. Then the cost to move this barge loaded with grain from Minneapolis, Mn would be $12.38 per ton or $0.372 cents per bushel for wheat and soybeans. Corn would be $0.346 per bushel. As with other commodities, barge freight rates follow a season pattern with rates usually at a low in the summer and high during the harvest season. As described above barges are traded in a open market environment. A shipper can acquire a barge either through direct dealings with a barge operator or through a broker. In addition to short term spot purchases of barge freight, a shipper might arrange a long term contract with a barge operator lasting several months or even several years. The price of the freight might be fixed at a certain level but more likely the rates will fluctuate based on some benchmark of the barge freight rates. Barges move a major volume of agricultural commodities to export markets. There is a lot of commodities that move from port to port in the entire river system everything from salt to coal to steel as all freight is market driven. | 
