Aren’t all the minerals necessary for plant growth already in the soil?
In most cases, no. The world’s cropland has been under cultivation for many decades and each crop cycle removes trace minerals from the soil or the elements are lost through erosion. Since most fertilizer programs only replace N, P and K, crops become deficient when the soil has been depleted of the trace elements. Of course, plants can complete their life cycle without the full range of minerals but they will not produce at their full potential or be healthy and adequately resistant to disease.
