Soil Fertility & Animal Health (The Albrecht Papers, Vol II )
Dr. William A. Albrecht, professor of soils at the University of Missouri College of Agriculture, was  first a student of nature, and his greatest credential was that Nature accepted his findings, worked with them, and delivered much of American agriculture from the bondage of ignorance. Dr. Albrecht traveled widely and studied soils worldwide. "You have to have a vision," Dr. Albrecht used to say. "Unless you do, nature will never reveal herself."  And such a vision he had. He showed that you need to feed the soil, not the plant. That animal health stems from the soil. And he developed base-level requirements for soil nutrients, formulas used to this.