Trump’s Tariffs May Risk U.S. Access to This Critical Mineral

As the U.S.-Canada trade war intensifies one of America’s greatest vulnerabilities is an unassuming mineral: potash. As a key source of potassium, potash is essential to plant growth, boosting crop yields, and preventing soil depletion—making it irreplaceable in modern industrial farming and vital to global food security. Without it, agricultural output would plummet, driving up food prices and exacerbating shortages. Yet with few domestic sources, the U.S. imports over 80% of its supply from Canada—making the mineral a potential economic weapon for Canada. Recognizing this vulnerability, Ontario Premier Doug Ford has floated the idea of cutting off U.S. exports entirely in response to the Trump administration’s promise of escalating tariffs.

Even President Donald Trump has belatedly recognized the importance of Canadian potash. In Feb., he lowered his initial 25% tariff to 10%. Yet Trump’s willingness to gamble with this critical resource stands in stark contrast to past leaders, who went to great lengths to secure these supplies.

Potash, technically a term for a variety of potassium-rich minerals, became essential in the 19th century as industrialization drove the need for chemical fertilizers. With soils depleted by intensive farming, and populations growing rapidly in urban centers, agriculture could no longer rely solely on traditional methods for accessing potassium, such as crop rotation and wood ash. Potassium, along with nitrogen and phosphorus, became one of the three key nutrients in modern fertilizer, and demand for it soared.

Germany, with vast deposits in places like Stassfurt, quickly became the dominant global supplier of potash. Long a pioneer in chemical fertilizer, Germany backed its industry with aggressive state intervention. In the early 20th century, the government forced all domestic producers into a centralized, state-supervised cartel. This allowed Germany to regulate output, fix prices, and undercut international competitors—consolidating near-total control over the global potash market and leaving other nations dangerously dependent.

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The risks of this monopoly became clear during World War I, when Germany cut off exports to weaken the Allies. It worked. The price of potash soared fifteenfold. As countries scrambled by tapping into fertilizer reserves and using alternatives such as sea kelp, the embargo put a serious strain on global food supplies. Potash also was an essential ingredient in gunpowder, adding to the strain of the embargo.

The wartime potash shortage left an indelible mark on other European nations, which emerged from the conflict determined to secure their own supplies. For France, the answer lay in Alsace—a region it had previously controlled and the location of a major potash mine once integrated into the German cartel. When Alsace was returned to French control under the Treaty of Versailles, French authorities quickly seized the mine and took over operations, transforming it into a reliable domestic source and a safeguard against future foreign dependence.

Britain, however, had no such ready solution. Lacking domestic reserves, its leaders looked farther afield—to the Dead Sea, whose mineral-rich salts contained one of the world’s most promising untapped sources of potash. The region around the Dead Sea (part of the Ottoman Empire prior to WWI) held enormous economic appeal for imperial powers; a 1929 New York Times article estimated the Dead Sea’s salts to be worth a staggering $100 to $200 billion—in 1925 dollars. One member of the UK’s House of Lords, Viscount Templeton even described the Dead Sea, Haifa Bay, and the Jordan Valley as a “unique industrial trilogy,” arguing that their value made “permanent British control” essential.

The economic promise of Dead Sea potash played a key role in Britain’s insistence on governing Palestine after World War I. But extracting the mineral posed a challenge. Elsewhere, potash was mined from rock, while its viability as a large-scale waterborne extract remained uncertain. Rather than take on the financial risk directly, Britain sought private investors, offering a monopoly concession to exploit the Dead Sea’s resources—a move that would allow private capital to absorb the risk while the empire reaped the benefits.

The strongest bid for the Dead Sea potash concession came from Moshe Novomesky, a Siberian engineer and the only applicant with a proven extraction method. Backed by deep-pocketed New York investors from the Palestine Economic Corporation, Novomesky had already built a small experimental plant that successfully demonstrated a low-cost process for extraction that relied on solar evaporation of Dead Sea waters. His results convinced British officials in Palestine that he was the best choice to secure this critical resource.

Yet Novomesky’s bid also posed a problem: he was Jewish and an active Zionist. British officials fearedhis loyalties lay more with the Zionist movement than the Empire—a concern that blended legitimate strategic considerations with antisemitic suspicions of Jewish disloyalty. More pressing, they worried that granting such a lucrative concession to a Zionist would inflame Arab opposition.

To ease British concerns, Novomesky partnered with several respected British citizens—Major Thomas Gregorie Tulloch, and Victor Bulwer-Lytton, the second Earl of Lytton—and agreed to various export and production guarantees. While this reassured London of his loyalty, it did little to address the second problem. Still, the value of an independent potash supply outweighed the risks. Despite significant parliamentary pushback, Britain awarded Novomesky the concession, convinced he was the best option to develop the resource.

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That decision proved economically sound for the British. Novomesky’s company, Palestine Potash Limited, exceeded its production quotas, vindicating British faith in his methods. But fears of unrest were well-founded. As historian Jacob Norris has shown, Palestinian Arabs viewed the concession as yet another example of British favoritism toward Zionists and a plundering of their country’s resources, fueling nationalist anger and Palestinian unrest. Britain even faced the threat of embarrassing potential legal challenges to the concession in The Hague.

Yet, despite the backlash, the government held firm and Britain’s gamble paid off when World War II broke out. As Germany once again cut off potash exports, Britain invoked an emergency clause in Novomesky’s concession, diverting nearly all Dead Sea production to the Empire. What had once been a geopolitical risk—investing in a Zionist-led extraction enterprise—became a strategic advantage, ensuring Britain’s uninterrupted supply of a critical wartime resource. While the conflict devastated numerous supply lines worldwide, Britain had secured its potash lifeline.

The lesson? The British Empire understood that securing a reliable supply of potash was essential to its survival. So essential that it subordinated other national goals to ensure access to the mineral—a kind of Britain First policy. While Britain’s rule in Palestine is rarely judged a success, its decision to prioritize potash helped Britain safeguarded its supply.

In contrast, Trump appears willing to gamble with the U.S. supply of potash, even as major alternative producers—Russia, Belarus, and China—pose geopolitical challenges. Meanwhile, Israel, a U.S. ally, supplies only 5% of the global market, and its reserves, still harvested through Novomesky’s solar evaporation method, are literally drying up.

Jacob Beckert is a doctoral candidate at the University of Washington, Seattle, where he researches American investment in Mandatory Palestine and its ties to capitalism and conflict in the region.

Made by History takes readers beyond the headlines with articles written and edited by professional historians. Learn more about Made by History at TIME here. Opinions expressed do not necessarily reflect the views of TIME editors.