Nitrogen deficiency is one of the major factors involved in declining soil fertility and land productivity in the HKH region. Use of chemical nitrogen fertiliser is often not possible, not desirable, or too expensive, but nitrogen-fixing plants can provide a simple solution. This book provides a brief description of the principles of biological nitrogen fixation, the different types of nitrogen-fixing plants, and the major potential uses of these plants to support agricultural development in the HKH region. Separate sections are devoted to various means of improving soil fertility, soil conservation, rehabilitation of degraded land, development of woody fodder, development of fuelwood crops, the use of terrace risers, and other uses of nitrogen-fixing plants.