An Introduction to Soil Humic Substances -- Roles of Organic Matter Minerals and Moisture in Sorption of Nonionic Compounds and Pesticides by Soil -- Variations Between Humic Substances Isolated from Soils Stream Waters and Groundwaters as Revealed by 13C-NMR Spectroscopy -- Effects of Humic Substances on Plant Growth 1 -- Ecological Aspects of Soil Organic Matter in Tropical Land Use -- Humic and Fulvic Acid Fractions from Sewage Sludges and Sludge-amended Soils 1 -- Application of Nuclear Magnetic Resonance Spectroscopy to Organic Matter in Whole Soils -- Humic Substances in Soil and Crop Sciences: An Overview -- Subject Index -- Synthesis and Degradation of Natural and Synthetic Humic Material in Soils -- Selected Methods for the Characterization of Soil Humic Substances -- Nitrogen in Humic Substances as Related to Soil Fertility1 -- Front Matter