Fundamentals and Functions of Soil Environment

Soil is a complex and dynamic natural system. The definition of soil varies widely, as it is dictated by its use and how we perceive it as a society for providing services, food, habitat, and enjoyment, where these functions are essential to soil health or quality. One well-established definition of soil is a medium that includes minerals, organic matter, countless organisms, liquid, and gases that together support life on earth through many services. Soil environment and functions are influenced by the parent materials and forming factors that contribute to the physical, chemical, and biological characteristics of soils. This chapter addresses the basic soil physical, chemical, and biological properties and explores the interrelationships between different soil properties and functions as essential building blocks for a healthy functioning soil system. The soil physical environment includes components of soil structure, aggregation, soil water potential and water movement, and soil thermal regime, along with governing forces. The soil biological environment includes all soil organisms (macro- and microorganisms), soil-plant relationships (plant root-soil interactions), plant growth and soil microorganisms, and plant root interface and nutrient cycling. In addition, the soil chemical environment discussion focuses on soil nutrient capacity and supply, nutrient cycling, and nutrient pathways and mechanisms.