The soil is the source of all agricultural products. To his knowledge of it and its management the farmer must owe much of his success. It is important then, that the principles underlying soil management should be given a definite and thorough study at the beginning of the course in Agriculture. It has been our aim to set forth the essential principles of the management of the soil in such a manner that the student may grasp them at the outset. It is intended that the students shall carefully work out the experiments and problems for themselves, especially those adapted to the region in which the school is located. Such work will mean infinitely more than lectures by the teacher and will be much longer remembered. We know that there are different opinions upon some of these topics, but we have tried to give only those con elusions verified by experience or supported by authorities which are among the best. We are indebted to Dr. John A. Widtsoe, president of the University of Utah, and a widely known authority on agriculture in the irrigated and the dry-farming regions of the West, for the reading of the manuscript, and for helpful suggestions.