In 2008 fertilizer prices went up $200 to $300/ton and the world is still around.
Actually world wide food riots started when fertilizer hit that number last summer. Several hundred million more were put into the starvation category. Which was more driven by oil costs because it is a flow through to all commodities. Though, phosphates are becoming an issue as well.
Actually, at this point. Massive world wide famine is inevitable to some magnitude higher than it has ever been.
Mostly driven by oil scarcity and soon water scarcity.
Anything that drives up oil prices, brings famine.