Integrated Fundamentals of Soil Science: Processes, Properties and Sustainable Management

Soil is a biologically complex system in which microbial and faunal communities regulate decomposition, nutrient cycling, soil structure, greenhouse-gas fluxes and pollutant transformation. This chapter synthesises the major organismal groups that constitute soil biological communities, including viruses, archaea, bacteria, fungi, protists, nematodes, mesofauna and macrofauna, and examines their ecological roles within the soil food web. It further explains how extracellular enzymes connect biological diversity with measurable biogeochemical processes through carbon-, nitrogen-, phosphorus- and sulphur-acquiring enzyme activities. Particular attention is given to microbial transformations of carbon, nitrogen, phosphorus and sulphur, including biological nitrogen fixation, nitrification, complete ammonia oxidation, denitrification, dissimilatory nitrate reduction to ammonium and anaerobic ammonium oxidation. The chapter also evaluates biofertilisers, including rhizobial inoculants, arbuscular mycorrhizal fungi and plant growth-promoting rhizobacteria, as tools for improving nutrient availability and reducing dependence on synthetic inputs under appropriate site conditions. Finally, it reviews soil pollution and bioremediation strategies for organic contaminants, heavy metals and emerging pollutants, with emphasis on microbial degradation, phytoremediation, rhizoremediation and technology-enabled monitoring. Overall, the chapter presents soil biology and microbiology as an integrated foundation for sustainable soil management, linking biological mechanisms with agronomic productivity, ecosystem services, soil health assessment and environmental restoration.