Seed inoculation is the practice of effectively introducing a high number of nitrogen-fixing bacteria (Rhizobium or Bradyrhizobium) on the surface of legume seeds prior to planting. The bacteria penetrates the root, resulting in the formation of root nodules that fix nitrogen from the air, and make it readily available to the plant. This book describes the need, the development and the use of rhizobia, and how this process may be reproduced successfully around the world, especially in underdeveloped agricultural countries.