A general knowledge of the problems involved in the maintenance of soil fertility is essential to a permanently successful agriculture in any region and among any people. Whether the predominating industry is grain farming or livestock farming, or a combination of the two, its foundation is the soil. In its broadest Sense the term soil fertility refers to the productive capacity or crop producing power of any soil under given climatic conditions, and it is the resultant of many factors or forces.

The soil chemist has given us a definite conception of what constitutes plant-food, and the soil physicist has contributed many valuable and practical discoveries to the rapidly increasing fund of knowledge concerning soils. It is known that suitable moisture and temperature conditions are essential, not only for absorbing and assimilating plant food, but also for rendering the plant food of the soil available. More recent research by the soil bacteriologist has revealed the fact that bacteria play an exceedingly important role in the problem of soil fertility, and it is undoubtedly true that the importance of these minute organisms is as yet but little understood and little appreciated, even by those most familiar with soil bacteriology. Excellent results are constantly issuing from soil laboratories and discoveries are being made which throw light upon problems observed in the field.