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The environment where an animal, plant, or microbe lives and grows.

Harvest index

Fraction of fresh matter, dry matter, N, P or K allocated to the harvested crop fraction(s).


One of the layers that form in the soil profile as a result of soil-forming processes. A horizon can appear as a defined visible layer. Single layer in soil profile with similar properties or material but which differs at least in one property, e.g. colour or texture from adjacent horizons above or below in the profile; diagnostic horizon: Dominant soil property or material defines name of horizon, e.g. gypsic horizon having distinct calcium sulfate (gypsum: CaSO4) enrichment; genetic horizon depending on the type of pedogenesis.

Human health

The effects of SICS with respect to humans can be either beneficial (proteins, vitamins) or toxic.

Human time scale

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.

Hydraulic conductivity (Ksat)

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

Hydromorphic soils

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.)

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