In this book, the authors present current research in the study of the ecology, production and disease management of the Alfalfa plant. Alfalfa appears to be one of the most interesting of the green crops, since it has high protein content and belongs to a group of major forage crops due to this high productive potential and excellent quality of green biomass. It is an important leguminous crop grown in many countries and has several important roles in different aspects of agriculture which include livestock feed and soil conservation. The authors of this book also explore the biological nitrogen fixation, symbiosis, which contributes greatly to the nitrogen nutrition source on earth.