The final 230 miles of the Mississippi river have long reinforced American might in global food markets. Ten grain terminals tower like fortresses along its bends, receiving crops from upstream farms, banking them in concrete silos and sending them over the levees into the holds of foreign ships. Together they can export 500,000 tonnes a day.

Yet this year the autumn high season never came. The amount of grain and oilseeds moving through Mississippi river ports has dropped by 9 per cent since the autumn of 2017, according to the Federal Grain Inspection Service. Buoys for mooring vessels bob unused.

Cargill, the world’s biggest agricultural trading house, repeatedly idled its two terminals on the river, including a five-day shutdown in November when workers stayed home unpaid.