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Anaerobic soil

Soil characterized by the absence of oxygen molecules (Fe3+, Mn4+, NO3-, SO42- are secondary electrons acceptors).


Particle with a negative charge. See also ion, cation.

Anion exchange capacity

Sum of exchangeable anions that a soil can adsorb. Usually expressed as centimoles, or millimoles, of charge per kilogram of soil (or of other adsorbing material such as clay).


An underground layer of permeable rock, sediment, or soil that yields water

Arable land

Agricultural land that is cultivated by ploughing, usually to 20 or 30 cm depth. More than 30 cm represents deep ploughing.


The process of development of a layer of coarse particles on the surface of a soil which is capable of protecting the soil below from wind or flowing water.


The direction that a slope faces, measured at right angles lo the contour.

Available water storage capacity

Corresponds to the water retained in the soil between the states of field capacity (FC) and permanent wilting point (PWP)


The diversity of living organisms in any one place.


The quantity of living material present at a given time within a given area.

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