The Globe and Mail reports in its Saturday, March 1, edition that over 80 per cent of the potash used by U.S. farmers comes from Canadian mines, and costs may skyrocket with potential tariffs. The Globe's Kate Hellmore writes that in Saskatchewan, a machine is boring into the Earth 1,000 metres deep, seeking a key compound for global food production amid Canada's trade tensions with the U.S. This machine, launched recently, operates via a fibre optic connection from a climate-controlled office above ground. This tunnel, known as a face, cost $30-million and is part of a network across six mines owned by Nutrien, Canada's largest mining company and a major agricultural supplier. Nutrien's key asset, potash, generated $3-billion (U.S.) in net sales last year. Since taking office in January, U.S. President Donald Trump has threatened a 25-per-cent tariff on Canadian goods, claiming the U.S. needs nothing from Canada. Despite that assertion, the U.S. does in fact need Canadian potash. Nutrien has the largest potash reserves and production volume in the world. The U.S. heavily relies on these sources, as only Russia and Belarus have smaller potash reserves, which are also vulnerable to geopolitical instability.