Everything ships in the same four months
The South American export calendar is unusually concentrated. Brazilian soybeans start moving in February, Argentine soybeans and corn from April, and the second Brazilian corn crop from July. For roughly four months, the same berths, the same trucks and the same vessel pool serve almost the entire hemisphere's exportable surplus.
The result is predictable and it happens every year: truck queues outside Rosario and Santos, waiting time at anchorage, and a freight market that reprices in weeks rather than months. A CIF offer quoted in February on a July shipment is exposed to that repricing unless the freight is fixed at the same time as the cargo.
What actually drives the spike
Three things move together. Vessel supply in the Atlantic basin tightens because tonnage is committed elsewhere. Port congestion extends turnaround times, which removes effective capacity from the fleet without a single vessel leaving the market. And upriver loading at Paraná ports depends on river draft, which in a dry year forces partial loading and topping off at deeper terminals — an extra leg, an extra cost.
None of this is unpredictable. What catches buyers out is treating the freight component as a line item to be filled in later rather than as a position to be taken at the same moment as the cargo position.
Practical responses
Buyers who plan around the window rather than into it get better outcomes. Booking freight and cargo together, even at a slightly worse cargo basis, removes the larger exposure. Shifting a portion of the program to Uruguayan terminals — Nueva Palmira in particular — trades a marginally longer inland haul for materially shorter waiting times. And for programs under 10,000 MT, containerised shipment often prices better than a small bulk parcel once demurrage risk is included honestly in the comparison.
The point is not that one route is always better. It is that the freight decision belongs at the front of the negotiation, not the end of it.