Rail will try, but doesn't scale as fast: tracks are not always running in the right direction, and the best maintained tracks are already busy. Eventually rail can have more capacity, but trucks can scale faster.
>tracks are not always running in the right direction
If the alternative is to let the grain rot, it does not matter much what direction the tracks run in; all that matters is that the the rail network connects some destination willing to buy the grain with where the grain is now.
A Mississippi barge is about 1,500 tons capacity, a truck is about 25/26 tons, and each rail car is about 100 tons. Barges are grouped in 15 barge tows, and trains are grouped in 90 to 125 car unit trains.
Its a bit easier to get the trains than that many trucks. Also considering that can do barges can almost always do trains. Its not ideal and barge would be preferred, obviously.
