Yields of most plants are higher in the tropics: there is more sunlight, more water, and no frost. Wheat, historically, hasn't been able to benefit from this as

Yields of most plants are higher in the tropics: there is more sunlight, more water, and no frost. Wheat, historically, hasn't been able to benefit from this as it wasn't adapted to the climate. Most minor minerals are present in plants to the tune of 0.001% by weight or less. We extract many times as much manganese, chromium, copper etc as the metal as we would from the soil. Selenium is generally postulated as the limiting element for life on Earth, but we're not yet at the point of needing to supplement it in soil. Brazil nuts are supposedly a particularly Se-avid crop, yet they haven't destroyed the ecosystem of Brazil so far. Soil depletion more generally consists of changes in texture (less water holding) and reduced ability to slow-release the nutrients we already add (NPK). It has been addressed by adding clays — chiefly aluminosilicates — which are predominantly composed of elements not utilized by living things (mostly). In other words, it's usually not the nutrients themselves being removed from a "depleted" soil, at least in the modern day.