Trace the energy and inputs behind a tonne of grain.
Wheat yields per hectare are several times what they were a century ago. What bought that?
Yes.Yield is purchased, not discovered. Nitrogen fertiliser in particular is made from natural gas, which is why fertiliser prices track gas prices almost exactly.
Not quite.Soil quality has generally not improved, and in many places has fallen. The yields rose anyway, on inputs.
Not quite.A small contributor in some regions. It cannot account for a multiple.
A modern crop is an energy conversion: gas into fertiliser, diesel into cultivation, sunlight into grain. The last step is free and the first two are not.
Put the chain in order: from a gas field to a loaf.
The most consequential supply chain most people have never heard of.Yes.It is why a gas crisis becomes a food story within a season. The link is not metaphorical — the nitrogen in the crop was, quite literally, made using gas.
Slide the fertiliser applied and watch what the field returns.
NoneModerateHeavyVery heavy
Yield2.5 t/ha
A well-fertilised field8.5 t/ha
NoneThe soil supplies what it has. Yields are a fraction of modern ones.
Yield6.5 t/ha
A well-fertilised field8.5 t/ha
ModerateThe largest gains come here. Each extra kilogram is still buying a lot of grain.
Yield8.5 t/ha
A well-fertilised field8.5 t/ha
HeavyYields still rise, and by much less. The surplus washes into rivers.
Yield8.6 t/ha
A well-fertilised field8.5 t/ha
Very heavyNo further gain. The extra is pure cost, and pure pollution.
Why does the last increment produce almost no extra grain?
Yes.Past the point where nitrogen is scarce, water, light or another nutrient becomes the constraint. Adding more of what is no longer limiting buys nothing — the same diminishing returns as everywhere else in this catalogue.
Not quite.The same product produced large gains at lower rates in the earlier frames.
Not quite.Heavy use does cause harm over time. Within one season the limit is simply what the plant can take up.
Move the control to see what changes.
Which of these move when energy prices move?
Nitrogen fertiliser.
Diesel for tractors.
Grain drying.
The rent on the land.
Greenhouse heating.
Yes.Four of five, which is why a gas price shock reaches the food system from several directions at once and why food inflation lags energy inflation by months rather than years.
A field yields 2.5 tonnes per hectare unfertilised and 8.5 fertilised. How many times higher is the fertilised yield?
times
Yes.8.5 ÷ 2.5. Roughly three times as much food from the same land — and the reason land use has not risen in step with population.
What does this imply about a fertiliser shortage?
Yes.The effect is delayed by a planting cycle and spread by trade. It is one of the clearest cases of a system where a disruption in one commodity arrives as a crisis in a different one, on the other side of the world.
Not quite.The frames above show what less produces. The early increments are the ones doing the work.
Not quite.Prices do adjust — by rising, which is the mechanism by which the shortage reaches households.
Lesson complete
Yield is bought with inputs, and most of those inputs are energy.