Soil sampling for microbiological analysis; Statistical treatment of microbial data; Soil sterilization; Soil water potencial; Most probable number counts; Light microscopic methods for studying soil microorganisms; Viruses; Recovery and enumeration of viable bacteria; Coliform bacteria; Autotrophic nitrifying bacteria; Free-living dinitrogen-fixing bacteria; Legume nodule symbionts; Anaerobic bacteria and processes; Denitrifiers; Actiomycetes; Frankia and the actinorhizal symbiosis; Filamentous fungi; Vesicular-arbuscular mycorrhizal fungi; Isolation of microorganisms producting antibiotics; Microbiological procedures for biodegradation research; Algae and cyanobacteria; Marking soil bacteria with lacZY; Detection of specific DNA sequences in environmental sample via polymerase chaim reaction; Isolation and purification of bacterial DNA from soil; Microbial biomass; Soil enzymes; Carbon mineralization; Isotopic methods for the study of soil organic matter dynamics ; Practical considerations in the use of nitrogen tracers in agricultural and environmental research; Nitrogen availability; Nitrogen mineralization, immobilization, and nitrification; Dinitrogen fixation; Measuring denitrification in the field; Sulfur oxidation and reduction in soils; Iron and manganese oxidation and reduction.