That portion of the pedogenic time scale that covers periods of centuries, decades, or less.

Process whereby the carbon of organic residues is transformed and converted to humic substances through biochemical and abiotic processes.

The well decomposed, amorphous, stable fraction of the organic matter in mineral soils with a low specific weight and high surface area; usually composed of many organic compounds of high molecular weight and dark colour. A term often used synonymously with soil organic matter. Humus is important for soil fertility, and helps to bind soil particles and aggregates together.

A quantitative measure of how easily water flows through soil. (Compare to infiltration and permeability.)

Formed under conditions of poor drainage in marshes, swamps, seepage areas or flats.

Long chains of cells formed by fungi usually occurring between aggregates rather than within micropores. (Compare to mycelium.)

The conversion by soil organisms of inorganic nutrients such as ammonium or nitrate into organic compounds that are part of their cells. This makes the nutrients temporarily immobile in the soil and unavailable to plants. (See mineralization.)

An instrument (measurement, dataset, model, expert elicitation system) for quantifying an attribute, providing quantitative information of the system. For instance, the protocol for soil sampling and pH (KCL) measurement is an indicator for the 'soil pH', and the extraction, counting, identification of nematodes and calculation of the maturity index is an indicator for the 'nematode community in the soil system'. Note that this definition differs from the daily practice where, for example, the pH or the nematode community as such, and not the protocol, is seen as the indicator.

A quantitative or qualitative measure used to estimate soil functional capacity. Indicators should be adequately sensitive to change, accurately reflect the processes or biophysical mechanisms relevant to the function of interest, and be cost effective and relatively easy and practical to measure. Soil quality indicators are often categorized into biological, chemical, and physical indicators.

Measures of living organisms or their activity used as indicators of soil quality. Measuring soil organisms can be done in three general ways: 1) counting soil organisms or measuring microbial biomass, 2) measuring their activity (e.g. soil basal respiration, cotton strip assay, or potentially mineralizable nitrogen), or 3) measuring diversity, such as diversity of functions (e.g., biolog plates) or diversity of chemical structure (e.g. cell components, fatty acids, or DNA). Each approach provides different information.