Nutrient-Element Balance by C. B. SHEAR and H. L. CRANE

B. rALANCE is a fundamental part of nature's law. But man's activities have a way of upsetting nature's balance and usually.it takes a serious unbalance to make us see the situation and try to correct it. Our increased concern over our own diets exemplifies an unbalance. The variety of foods that comprise the average normal diet should provide enough of the essential minerals and vitamins to meet our normal requirements. But not so. Many of the soils on which food crops are grown do not supply the plants with sufficient minerals to meet our needs or to enable the plants to synthesize vitamins in quantities to meet our demands. Further, and worse, we are not satisfied to use many plant products, particularly the cereals, in the form in which nature gives them to us, but demand that they be processed and "purified." These purifying processes remove some of the nutrients, and unless we know which and how much of the nutrients are removed, and supply them in our diets from other sources, we do not get enough of them. Much the same situation exists with respect to the nutrition of our crops. The soils upon which plants depend for their food materials developed from minerals, which originally contained a fairly wellbalanced supply of the essential mineral nutrients for the plants that became native to each soil. Plants with différent nutrient requirements developed on soils having different powers to supply nutrients. Many soils, in their virgin state, do not furnish a balanced nutrient supply for agricultural crops. Man, however, has not restricted his cultivation to the soils best suited to the crops he wants to grow, nor has he been careful to protect the soil from erosion and leaching. Furthermore, he has continued to crop the soil year after year and has failed to return to the soil all of the nutrients removed in the crops produced. The