Synopsis This book is based on the compilation of lecture notes on nuclear techniques in agriculture and biology, prepared and updated for students of PG School, IARI, New Delhi during the past 16 years. The book contains three parts, namely, Fundamentals of Nuclear Science (covering the basic features), Applications (Comprising essential application with focus on agriculture) and Appendices (Consisting of Bibliography, nuclear terms, radioactive decay charts, select constants and abbreviations used). Each of these parts is further divided into few chapters covering different aspects of nuclear tools and their applications in agricultural science. In short, the flowless presentation on various aspects of nuclear applications is expected to enrich biologists and agricultural scientists to easily understand not only the basic concepts but also essentials on the application of the nuclear energy in a variety of ways for research and in agriculture.