Fertilizer

Three nutrients feed the world

Almost half the people alive are fed by synthetic fertilizer. Strip it out and global crop yields collapse, because soils cannot replace, season after season, the nutrients that harvested grain carries off the field. The longest-running test of that is Broadbalk, a wheat field at Rothamsted in England sown every year since 1843: the strip that has never had fertilizer or manure still yields about 1 tonne a hectare, while fertilized plots of the same field yield 6 to 11, and agronomists put the share of world crop yield owed to commercial fertilizer at 30 to 50 percent at least. Three primary nutrients do the heavy lifting, and the industry shorthand for them is N, P, K, the chemical symbols for nitrogen, phosphorus, and potassium. Nitrogen builds protein and chlorophyll and drives green leafy growth; it is the volume nutrient, applied in the largest tonnages and exhausted fastest. Phosphorus, applied as phosphate, powers roots, energy transfer, and seed and fruit formation. Potassium, applied as potash, regulates water, disease resistance, and the quality of the harvest. Most bagged products are blends sold by their N-P-K ratio, and a farmer reads that ratio the way a trader reads a spread.

The world consumes roughly 200 million tonnes of fertilizer nutrients a year, split very roughly 55 percent nitrogen, 25 percent phosphate, and 20 percent potash. Fertilizer is the one place where energy, mining, and agriculture meet in a single product. Nitrogen is essentially natural gas turned into a solid; phosphate and potash are mined rocks upgraded into soluble plant food. So the fertilizer trader watches the gas curve, the sulphur market, a handful of mining jurisdictions, and the planting calendar all at once.

Before the factory: islands of bird droppings

For most of history a farmer kept soil fertile with what the farm itself produced: animal manure, human poop, ash, marl (clay with calcium carbonate, i.e. lime), seaweed and fish on the coasts, and crop rotation, above all planting clover, beans or peas every few crop plantings, since these legumes fix nitrogen from the air through bacteria on their roots. Farmers knew it worked for some two thousand years before anyone knew why: in 1886 the German agricultural chemists Hermann Hellriegel and Hermann Wilfarth showed that the nodules on legume roots take nitrogen from the air, and in 1888 the Dutch microbiologist Martinus Beijerinck isolated the bacterium responsible, now called Rhizobium. Even so, a farm could add only as much nitrogen as its own legumes fixed and recycle the rest, which capped yields. By the early nineteenth century Britain was importing crushed bones in bulk, mostly for their phosphorus, since bone is largely calcium phosphate with a few percent of nitrogen from its protein, enough that the German chemist Justus von Liebig complained England was robbing other countries of their fertility, digging up the battlefields of Leipzig and Waterloo for bone.

The breakthrough came in two steps. The Incas had used seabird guano for centuries and protected the birds, banning landings on the islands in the breeding season and, by the account of the chronicler Garcilaso de la Vega, punishing the killing of a guano bird with death. Europe noticed only when Alexander von Humboldt brought samples back from Callao in 1804 and the chemists Fourcroy and Vauquelin analysed them in Paris, but nothing much followed until 1840, when Liebig's book on chemistry in agriculture explained that plants feed on mineral nutrients such as nitrogen and phosphorus. That gave farmers a reason to pay for a concentrated dose, twenty barrels of guano reached England the same year, and by 1842 the London merchant house Antony Gibbs & Sons held Peru's contract to supply Britain, a fortune that produced a Victorian rhyme: William Gibbs made his dibs selling the turds of foreign birds.

So the first great fertilizer commodity was guano: seabird droppings piled up over thousands of years on islands too dry for rain to wash them away, rich in both nitrogen and phosphate. Peru's Chincha Islands held deposits reported at around 150 feet deep, left by cormorants, boobies and pelicans feeding on the anchoveta of the Humboldt Current. Between 1840 and 1880 Peru exported more than twelve million tonnes as a state monopoly, and guano supplied roughly 60 percent of government revenue. The digging was done in large part by about 100,000 indentured Chinese labourers shipped from Guangdong between 1849 and 1874, in conditions close to slavery. Spain seized the islands in 1864, and by the late 1870s the deposits were essentially gone.

The scramble went global. The United States passed the Guano Islands Act of 1856, letting any citizen claim an unoccupied island bearing guano, and eventually claimed about 94 of them; Baker, Howland, Jarvis, Johnston and Midway are still American territory because of it, and Navassa remains disputed with Haiti. When the guano ran out, the trade moved to sodium nitrate mined from the Atacama Desert (then divided between Bolivia and Peru), and the War of the Pacific (1879 to 1884) was fought largely over those deposits, costing Bolivia its coastline and Peru its southern provinces to Chile. What ended the whole business was chemistry: the Haber-Bosch process, industrialised in Germany from 1913, made nitrogen fertilizer from the air and natural gas, and no island or desert has mattered for nitrogen since.

The scale of that substitution is the most striking statistic in this group. Nitrogen is about 3 percent of the human body by weight, the backbone of every protein and strand of DNA, and estimates by Vaclav Smil and by Erisman and colleagues put roughly half the nitrogen in the people alive today as having passed through a Haber-Bosch plant on its way into their food. The nitrogen atoms themselves came from the air; what the natural gas supplied was the hydrogen and the energy that made them usable. So about one and a half percent of a typical person's body weight exists because methane (natural gas) was burned in an ammonia plant.

Nitrogen is natural gas in a bag

Nitrogen fertilizer begins in the air, which is roughly 78 percent nitrogen gas, but that gas is inert and useless to plants until it is fixed into a reactive form. The Haber-Bosch process, invented in Germany before the First World War, does exactly that: it combines atmospheric nitrogen with hydrogen at high temperature and pressure to make ammonia. The hydrogen comes from natural gas (methane), and that single input dominates the economics. Natural gas is roughly 60 to 80 percent of the cash cost of making ammonia.

Ammonia is the building block; almost everything else in the nitrogen complex is ammonia upgraded. React it with carbon dioxide and it becomes urea, the world's most traded solid fertilizer at 46 percent nitrogen. Combine ammonia with nitric acid, itself made from ammonia, and it becomes ammonium nitrate. Dissolve ammonium nitrate and urea in water and it becomes UAN, a liquid sprayed across the US Midwest. When European nat gas prices spiked through 2021 and 2022, ammonia plants across the continent simply switched off because the nat gas going in cost more than the urea coming out, idling capacity from the United Kingdom to Germany and sending urea to record highs. The lesson repeated in 2026, when Gulf nat gas feedstock and shipping were disrupted by the Strait of Hormuz crisis and urea ran back above 850 dollars a tonne.

Which form reaches the field depends on where the field is. Worldwide, solid urea dominates, about 57 percent of nitrogen fertilizer use by the International Fertilizer Association's 2013/14 count, up from 49 percent at the start of the century, spread as granules or prills and above all across Asia, from India and China to Pakistan and Southeast Asia, because it is the cheapest nitrogen to ship and store. The United States is unusual in having no single dominant form: farmers inject anhydrous ammonia straight into the soil as a pressurised liquid, which few other big markets do at scale, spray UAN through the same equipment as their herbicides, which lets them apply it during the season, and spread urea as well, each a substantial share. Ammonium nitrate on its own is now a smaller product, used mainly in Europe, Russia and on pasture, and its other life as an explosive, from Oklahoma City in 1995 to the Beirut port blast in 2020, means it is tightly regulated and banned outright in some countries.

Phosphate and potash are mined, not made

Phosphate starts as phosphate rock, dug from sedimentary deposits and dissolved in sulphuric acid to make phosphoric acid, which is then combined with ammonia to make the finished fertilizers DAP (diammonium phosphate) and MAP (monoammonium phosphate). Two inputs therefore matter beyond the rock itself: ammonia, which ties phosphate back to the gas market, and sulphur, a byproduct of oil refining and gas processing that becomes the sulphuric acid. World phosphate reserves are extraordinarily concentrated: Morocco's state producer OCP holds the majority of them, with China and the United States the other large producers, so phosphate carries a long-run resource-scarcity story that nitrogen does not.

Potash is the simplest of the three: it is mostly potassium chloride, known in the trade as MOP (muriate of potash), mined from ancient evaporite seams left behind by dried-up seas, then crushed and purified. There is no chemistry to speak of, just mining and concentration, so potash economics are about ore grade, mine depth, and freight. Supply is concentrated in a short list of countries: Canada (above all the Saskatchewan basin worked by Nutrien and Mosaic), Russia, and Belarus together hold most of the world's low-cost capacity. When sanctions hit Belarus and then Russia through 2021 and 2022, removing producers that together supplied roughly 40 percent of the market, potash prices spiked above 1,200 dollars a tonne before trade rerouted and prices normalized.

How it trades: hubs, agencies, and a planting calendar

Fertilizer is overwhelmingly an over-the-counter physical business priced against published assessments rather than a screen-traded futures market. The price reporting agencies do the work that an exchange does elsewhere: Argus, CRU, Profercy, and Fertilizer Week publish benchmark prices at the hubs where cargoes actually change hands. Urea is assessed FOB Egypt, FOB Middle East, and CFR Brazil; ammonia at Tampa CFR and at various FOB points; DAP at Tampa, Morocco, and Brazil; potash at Vancouver, Brazil, and Southeast Asia. A deal is struck as a netback to one of these hubs, and a producer's monthly tender, such as India's urea purchases or Brazil's import flow, can move the global price by itself.

Cleared paper exists but is thin. CME lists UAN and urea swaps (Nola and the US Gulf, Egypt, and Brazil) that let traders and farm cooperatives hedge, but the volumes are a rounding error next to crude oil or CBOT grains. The reasons are structural: fertilizer is bulky and differentiated by grade and location, contracts are seasonal, and a handful of national buyers dominate demand. Pricing swings hard around the planting calendar, firming ahead of spring application in the northern hemisphere and again ahead of the South American season, so the fertilizer year has a rhythm closer to a crop than to a financial instrument.

Why a price spike becomes a food crisis

It is tempting to wave fertilizer cost away, on the logic that a bag of urea is cheap next to the value of the harvest it grows. That intuition is wrong twice over. First, fertilizer is one of the largest variable costs in grain farming, not a footnote: it ran around a third of US corn operating costs through the 2020s and close to 40 percent at the 2022 peak, so a tripling of the price can lift total production cost by a quarter and turn a thin margin into a loss.

Second, and more important, in poor countries the damage comes through quantity, not price. A smallholder who pays for fertilizer upfront, often on credit, before the harvest does not quietly absorb a tripling and pass it on; that small farmer buys less or none. In 2022, after prices roughly tripled, more than 45 percent of fertilizer-using households surveyed across Burkina Faso, Ethiopia, Malawi, Nigeria, and Tanzania reported a shortfall, overwhelmingly because they could not afford it rather than because it was unavailable. Less fertilizer means lower yields on already-tired soils, which means less food and higher local prices: the chain that turns a fertilizer spike into a hunger problem. Sub-Saharan Africa already applies only about 22 kilograms per hectare against a world average near 150 and an agronomic target around 100, so it is yield-starved before any shock, and a price spike pushes it further from the optimum rather than merely trimming a margin. That asymmetry, a manageable cost for a capitalised farmer in Iowa but an applied-or-not decision for a farmer in Malawi, is why the 2026 Strait of Hormuz crisis, by disrupting a Gulf that supplies roughly 30 percent of globally traded fertilizer, was treated as a food-security threat and not merely a margin story.

Which raises an obvious question: why does aid arrive as bags of grain rather than fertilizer? For an acute famine, food is the only answer, hunger is immediate while fertilizer helps only the next harvest, and only bundled with seed, rain, and land, and grain reaches the landless and urban poor that an input cannot. But for chronic hunger the calculus flips, and agencies increasingly do fund fertilizer and seed: Malawi's input-subsidy programme briefly turned the country from maize importer to exporter, and AGRA, the African Development Bank, and US Feed the Future back inputs and agronomy over handouts. The reason in-kind grain dominated for so long is partly donor politics: US food aid has long been required to be bought from American farmers and shipped on US-flagged vessels, which also undercuts local farmers by dumping subsidized grain, the opposite of building the local production that fertilizer supports. The slow shift toward cash transfers and local procurement is the field moving from feeding people this month toward raising the floor for next year.