Anyone clever enough to process Urea into Urea Nitrate would have no use for the Potash or Phosphate fertilizers.
Exactly so.
Last I knew, the price of 11-52-0 was nearly $1200/ton in Nevada. Super-phos (phosphoric acid, which was about net 50% P), as a little cheaper, but not much.
Nitrate fertilizers go up/down with the price of natural gas to some extent, but the phosphates went up and stayed up. The only thing that will bring them down is demand destruction.
Processing into urea nitrate would net material for a whole lot of smaller bombs for use in soemthing on the order of the Indian massacre recently. An ANFO bomb would be a centerpiece to such a slaughter.