I believe Robotbeats calculations are lacking if the intent is to demonstrate how much fossil fuel energy is embodied in one unit (joules, calories, etc) of food:

-hydrogen is not a primary energy, no accounting for energy needed to produce 1kg of H2 gas -producing ammonia from hydrogen consumes energy -producing corn from ammonia requires more embodied energy than sunlight - other fertilizers, *cides, fuel and construction industrial sized agricultural machinery.

Only measuring the chemical energy in quantity of H2 vs the dietary calories in associated corn produced is incomplete model of fossil fuels required in agricultural production.

If you are saying the urea price spike has occured in a complete isolation, like temporary specific failure of urea manufacturing , maybe its not a problem. If its one of the first noticable effects of an overall fossil fuel shortage, its going to have huge feedback effects invalidating economic models such as slowing renewable growth, making the whole economy less productive.