ABSTRACT
Soil solids, comprising inorganic and organic components, form the matrix or the body of most soils. This matrix, or the visible part of the soil, is the storehouse of water and nutrient elements (e.g., N, P, K, Ca, Mg, Zn, Cu, etc.). It is also the site of most processes that govern soils buffering and filtering capacity, and life support capability. The buffering capacity of the soil refers to its ability to withstand or to adapt to sudden perturbations such as in soil reaction (i.e., pH). The filtering capacity refers to soil’s ability to remove pollutants (e.g., pathogens or chemicals including heavy metals) out of the water percolating through the soil by denaturing pollutants or mechanical sieving of suspended particles. Both buffering and filtering capacities depend on soil’s reactivity. The latter refers to chemical, physical, and biological reactions in soil and depends on its nature (e.g., relative proportion of the inorganic and organic components, coarse or fine size, small or large surface area, and low or high charge density). Soil quality is determined by these and other properties of soil solids, which in turn moderate the soil’s ability to support plant and animal life. Soil’s life support capability depends on processes that govern productivity, elemental cycling, and environment quality (see Chapter 1).
