The world has made remarkable progress in maintaining adequate food supplies during the past quarter century by introducing yield-increasing technologies such as better genetics, crop protection products, and more efficient use of fertilizers and irrigations. Far more people depend on irrigation in the modern world than during the times of ancient Sumeria. The spread of irrigation has been the key factor in increasing global crop yields. But future scarcity present the single biggest threat to future food production. The shift of water from agriculture to the growing cities and industry almost certainly will impact global food production. This means that dryland agriculture will be increasingly important in meeting food requirement for the growing population. Advaces in plant genetics and agronomic conservation technologies, when considered in concert, continue to provide the greatest opportunities to achieve sustainability and profitability in dryland agriculture and will continue to be the focus of the ARS research program. The ARS is please to join the crop Science Society of America and international center for Agriculture Research in Dry Areas (ICARDA) in sponsoring a symposium “Challenges and strategies for Dryland Agriculture” at the Trisocieties Annual Meeting in November 2002 at Indianapolis, IN. This special publication contains an impressive series of paper by international group of experts on dryland agricultural production, conservation, and policy. The principles, philosophies, and technologies presented in this publication have the potential to contribute to improve food security and livelihoods for the people in dryland regions of the world.

From the beginning of agriculture until about 1950, increased food production came almost entirely from expanding the cropland base. Since 1950, however, the yield per unit of land area for major crops has increased dramatically. Much of the increase in yields was because of increased inputs of energy. Between 1950 and 1985, the farm tractor fleet quadrupled, world irrigated area tripled, and use of fertilizer increased ninefold. Between 1950 and 1985, the total energy used in world agriculture increased 6. 9 times. Irrigation played a particularly important role in the rapid increase in food production between 1950 and 1985. The world's irrigated land in 1950 totaled 94 million hectares but increased to 140 million by 1960, to 198 million by 1970, and to 271 million hectares in 1985. However, the current rate of expansion has slowed to less than 1 % per year. The world population continues to increase and agricultural production by the year 2000 will have to be 50 to 60% greater than in 1980 to meet demands. This continued demand for food and fiber, coupled with the sharp decline in the growth rate of irrigation development, means that much of the additional agricultural production in future years must come from cultivated land that is not irrigated. Agricultural production will be expanded in the arid and semiarid regions because these regions make up vast areas in developing countries where populations are rapidly rising.

Cover crops slow erosion, improve soil, smother weeds, enhance nutrient and moisture availability, help control many pests and bring a host of other benefits to your farm. At the same time, they can reduce costs, increase profits and even create new sources of income. You¿ll reap dividends on your cover crop investments for years, since their benefits accumulate over the long term. This book will help you find which ones are right for you. Captures farmer and other research results from the past ten years. The authors verified the info. from the 2nd ed., added new results and updated farmer profiles and research data, and added 2 chap. Includes maps and charts, detailed narratives about individual cover crop species, and chap. about aspects of cover cropping.

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Filled with figures, images, and illustrations, Encyclopedia of Water Science, Second Edition provides effective concepts and procedures in environmental water science and engineering. It unveils a wide spectrum of design concepts, methods, and solutions for enhanced performance of water quality, treatment, conservation, and irrigation methods, as well as improved water efficiency in industrial, municipal, and agricultural programs. The second edition also includes greatly enhanced coverage of streams and lakes as well as many regional case studies. An International Team Addresses Important Issues The only source to provide full coverage of current debates in the field, the encyclopedia offers professional expertise on vital issues including: Current laws and regulations Irrigation management Environmental water economics Agroforestry Erosion control Nutrient best management practices Water sanitation Stream and lake morphology and processes Sharpen Your Skills — Meet Challenges Well-Armed A direct and reliable source for best practices in water handling, preservation, and recovery, the encyclopedia examines challenges in the provision of safe water supplies, guiding environmental professionals as they face a worldwide demand for sanitary and affordable water reserves. Also Available Online This Taylor & Francis encyclopedia is also available through online subscription, offering a variety of extra benefits for researchers, students, and librarians, including: Citation tracking and alerts Active reference linking Saved searches and marked lists HTML and PDF format options Contact Taylor and Francis for more information or to inquire about subscription options and print/online combination packages. US: (Tel) 1.888.318.2367; (E-mail) [email protected] International: (Tel) +44 (0) 20 7017 6062; (E-mail) [email protected]

This publication discusses the processes above, within and below the soil that enable water to move and crops to grow, and is intended to help land users make better use and take better care of these basic resources. It aims to provide a solid basis for sound, sustainable soil moisture management. This document has been made more user-friendly by presenting a guide for field workers with activities, exercises and discussion topics in non-technical language, and by interspersing the text with illustrations and diagrams. The complete materials of this guide are included on the CD-ROM that accompanies this document