1. Introduction
2. Biochemistry of Humus Formation
3. Transformations of N, P, S
4. Chelation Reactions in Soil
5. Adsorption of Organic Compounds by Clay
6. Role of Organic Substances in Pedogenic Soil Aggregation Processes
7. Clay Organic Complexes
8. Humus-Pesticide Interactions in Soil
9. Role of Organic Matter in Carbon Sequestration