I actually didn’t know that about fertilizer

Because it's not true, nitrogen typically gets fixed from the air via the Haber Bosch process into ammonia for fertilizer, which specifically uses methane, aka natural gas, to produce hydrogen, not crude oil. I dunno how much natural gas exactly gets shipped on freight ships, but I'm pretty confident it's a tiny fraction compared to what goes through fixed pipelines. You do need phosphates for fertilizer too, and a sizable amount of phosphate salts are shipped from north Africa, but that only makes phosphate a shipping problem going China's way, not to us.