This book dwells on soil organic matter in its entirety: the composition, distribution, pools and reactive functional groups of soil organic matter; its decomposition, nutrient transformations and biochemistry of humus formation; its role in pedogenic processes; adsorption of organic compounds by clay; clay-organic matter complexes; humus - trace metals and humus - pesticides interactions; environmental significance of humic substances and characterization of soil organic matter. The potentials of nuclear techniques in the study of soil organic matter have been elucidated for the benefit of research scholars. Various management practices for building organic matter in soils have also been discussed. A compilation of qualitative and quantitative analytical procedures on organic matter complements the book. The book will be a useful source material for researchers, scholars and all stakeholders concerned with soil organic matter and sustainable agriculture.