The study of soil erodibility has become of paramount interest in the last few decades. The effects of soil erosion are serious and extensive and affect nearly all people.

Recent reports from many parts of the United States indicate that the so- called zinc - deficiency disease is wide spread. It affects some varieties of trees in some areas and all varieties in other areas, and occurs from Florida westward to the Pacific coast and northward to the Canadian line. Although the disease is more prevalent in trees, it is also known to affect annual plants.

Frequently, in evaluating plant deficiencies, one considers only those soil factors which are associated with the fertility of the soil-- mainly the levels of phosphorus, potash, nitrogen, and organic matter. A certain level of nutrition is essential for plant growth, but in order for the nutrients to exert their maximum influence on the productivity of the soil, it is equally important that a good soil environment be provided and maintained. A good environment requires that good physical conditions of soil, sir, and water be in balance.