Fertilizers, Pesticides, Herbicides and Insecticides: The reduction of minerals in our food is the result of using pesticides and fertilizers that kill off beneficial bacteria, earthworms, and bugs in the soil that create many of the essential nutrients in the first place and inhibit the uptake of nutrients into the plant.
Fertilizing crops with nitrogen, phosphorus and potassium has led to declines in magnesium, zinc, iron and iodine. Lower magnesium levels in soil also occur with acidic soils and around 70% of the arable land on earth is now acidic.
Thus, the overall characteristics of soil determines the accumulation of minerals in plants.