Soils consist of solid, liquid, and gaseous phases. They are in intense contact with both precipitation and groundwater as well as the atmosphere and serve as the substrate for plants. Complex chemical and physical—mostly quasi-dynamic—equilibria form the basis for assessing the suitability of a soil for agricultural use, which must be intensified in light of rising population numbers. The now available, completely revised 4th edition introduces the fundamental physical processes in soils and demonstrates how changes in physical properties and parameters (e.g., grain size, density, permeability, load) affect the stability and productivity of soils. The key processes of the movement of water, gas, and heat, as well as interactions with the solid phase, are detailed at various scales.