Soil organic matter research generally covers a wide range of phenomena involving numerous parameters. Some aspects of the research are fundamental and theoretical, others are applied and practical. The aim of this book is to provide a balanced account of some recently reported research with particular emphasis on new information, novel methods of analysis and changes in approach to outstanding problems. The contents comprise 35 papers differentiated into five themes, two of which are basically fundamental and the others applied. Research progress in the fundamental themes such as composition and structure of soil organic matter and turnover of soil organic matter tends to be slow. This is due to the complexity of the individual humic substances, humic acid, fulvic acid and humin, in the former and to the multiplicity of variable influences such as climatic conditions, agricultural systems, plant associations, soil textures and pH levels in the latter. The applied themes - on the effect of soil organic matter on soil structure, soil fertility and water quality, respectively - achieve more rapid advances due to the pressing needs of agriculture and the management of the environment. These are illustrated by the effects of soil organic fertility to aid better land use, and increasing the absorption of chemical pollutants to provide water of higher quality. New soil organic matter data can also be used as concomitant information for interpreting nitrogen research involving organic nitrogen in chemical and biological equilibria. Throughout the text, there are numerous accounts of experimental procedures and instrumentation. These developments have further substantiated the concept of humus quality, especially in relation to enzymic activities which presage changes in humus levels under different soil management. Intermixed with classical field crop and afforestation experiments are reports on investigations into subjects of public interest, such as characterization of the unstable soils of the Amazon Basin.