FROM THE PREFACE: Many aspects of range development and improvement have been extensively researched in the United States and Canada since World War II. While this has resulted in a rather voluminous literature on this phase of range science, the data have remained widely scattered in various journals, bulletins, handbooks, and research reports. Although individual chapters in a limited number of textbooks have dealt with range improvements and closely related subjects, no known effort has previously been made to bring this information together under one cover. Range Development and Improvements has as its goal the survey of this scientific field, the selection of principles and results, and the organization of this information into a useful and readily accessible form. Dr. L. A. Stoddart and Dr. C. Wayne Cook, my former associates in the Department of Range Science, Utah State University, provided the original idea for the textbook on range improvements. My teaching courses in range improvements at Utah State University and Brigham Young University and associated extension and research in the Intermountain Region and in the Great Plains provided the impetus for developing this idea into an active plan. The basis of this book, however, is the written reports of many people in range science and related fields. The society for Range Management, through its 5500 members, has actively promoted the advancement of grazing land management including improvements. Additional professional organizations associated with weed science, ecology, agronomy, animal science, wildlife science, soil conservation, and farm and ranch management have also promoted certain aspects of range improvements. A unique interagency organization active in the field of range improvements is the Vegetative Rehabilitation and Equipment Workshop (formerly Range Seeding Equipment Committee). This committee was organized to evaluate and develop better equipment and methods for range seeding, weed and brush control, and related range improvements. In cooperation with private and governmental equipment-development centers, many important contributions have been made on range-improvement equipment. The membership of this committee has come principally from the public land managing agencies but also from various universities, research organizations, and commercial enterprises. In developing this textbook and reference manual, I have attempted to include both principles and practices. Principles have been emphasized since these are the basis of solving the varied problems found on rangeland and of achieving high levels of productivity. Rigid formulas lack sufficient flexibility for uniform applications. However, stepwise procedures recommended in certain instances have been included to exemplify the adaptation of principles to applied range improvement. Basic principles provided in this manual should allow its use over broad geographic areas. Regional aspects over the United States and adjacent areas in Canada and Mexico have been emphasized, however. Local aspects of range improvement have frequently been referred to as a means of making geographic association. Helpful comments and suggestions on the content and format of Range Development and Improvements were received from many reviewers. Many of the pictures and drawings used in the book were provided by various agencies, organizations, and individuals; acknowledgement is made in the respective figure captions. This work should continue to prove useful not only as a textbook but also as a reference manual for ranchers, range technicians, public land administrators, agribusiness personnel, educators, and students. Range improvement is a rapidly advancing phase of range management. Researchers in the state agricultural experiment stations, the Forest and Range Experiment Stations, the USDA-Agricultural Research Service, and various private research foundations are continually adding to information available in this field.