An Arkansas Extension article says halted barge traffic on the Mississippi, whether from flooding or drought, tends to weaken soybean basis. Last October, low river levels pushed soybean basis to $1.25 under harvest futures, a dollar below the five-year average.
In April, a flood spike to 23 feet at McGregor, Iowa pushed basis negative at Elaine, Arkansas before it recovered to zero.
Barge disruptions weaken cash soybean bids relative to futures because elevators cannot move grain efficiently, lowering farmer returns and raising feed buyers' procurement cost sensitivity to river conditions.
After 297 past bearish logistics events, Soybeans moved a median +0.3% over 5 sessions (54% higher; middle half -1.5% to +1.8%), and +0.7% over 20.
Not enough comparable past events yet for a historical read.
Moves of each commodity's benchmark from the last close before the event. Historical reads pool past events of the same kind; they describe what happened, not what will. Not investment advice.