Adequate food supplies and a reasonable quality of life require energy~both noncommercial and commercial forms. This book is intended to be a reference for individuals who want a comprehensive overview of energy for agriculture, many of whom are located in remote areas with limited library resources. The purpose is to put energy for agriculture in perspective by presenting numerous national and regional examples of energy usage. Since the early 1970s, world petroleum prices have fluctuated from $3/barrel to more than $40/barrel in 1981 and then back to less than a half of the peak price today. Commercial energy is expensive at any price for rural villagers in developing countries, and energy prices in these countries do not necessarily correspond with world prices. For example, diesel fuel prices in some developing countries have increased, while world oil prices have decreased. The rural sector of developing countries depends heavily on noncommercial energy sources. Availability of noncommercial energy is highly site-specific. This book deals extensively with noncommercial energy~its sources, the technologies for converting energy to more useful gaseous and liquid forms, and its ultimate end uses. Chapter I is an introduction and overview. It emphasizes the essential nature of energy to supplement the limited work output of human beings. Chapter II describes energy use in world agriculture with particular emphasis on fertilizer, machinery, and irrigation. It tabulates cereal grain yields as related to commercial energy input for various regions. Chapter III presents numerous national and regional illustrations of energy use.