This book presents the English translation of "Organic Chemistry in Its Application to Agriculture and Physiology", a foundational work by Justus von Liebig (1803–1873), the father of modern agrochemistry and mineral fertilization, along with expert commentary. At just 21, Liebig—recommended by Alexander von Humboldt —was appointed professor of chemistry at the University of Giessen. There, he perfected elemental analysis and pioneered the isolation and synthesis of organic compounds. In connection with an invitation from the British Association for the Advancement of Science in Liverpool, Liebig travelled through England and Ireland, visited numerous chemical factories. This journey inspired him to explore applied chemistry, and in 1840, he authored "Organic Chemistry in Its Application to Agriculture and Physiology", the text reproduced in this volume. In this work, Liebig laid the foundation for agricultural chemistry, introduced the concept of the carbon cycle, and ignited debates that reshaped scientific thought. Essential reading for scholars, students, and enthusiasts, this volume offers deep insight into the history of chemistry and its lasting impact on agriculture and environmental science.