Basically, since transactions were done using SWIFT, the US companies had a lot of visibility into who was selling what and for how much. This allowed farmers to have a good idea of what crops were in demand and how much to plant for the season. Now that transactions are being increasingly done outside SWIFT, they're opaque to the west making it much harder to predict what demand is like.

the process of determining the price of a commodity in the marketplace through the interactions of buyers and sellers. in this case farmers are trying to forecast what the price will be after the growing season