Explosives are surely up in revenue now (double, triple?) and the world is using about every drop of production for both (as with every supply chain).

So, a +/- of $3B is a 16% shock to the fertilizer market. That is plus one year of explosives, but if you are going to war, you might need several years, all at once (pow). We are talking about future prices in the grand scheme.

That is in gross, too, we don't know specific chemical or supply bottlenecks: one kink in ammonia might not mean much except for fertilizer production; if ammonia is produced via hydrocarbon extraction, then fertilizer is not only dependent on energy prices, but competing directly with wartime energy supply.