Glossary

Main category for all glossary items


 

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Salinization

Process involving an accumulation of salt in the topsoil


Salt-affected soil

Soil that has been adversely affected by the presence of soluble salts, with or without high amounts of exchangeable sodium. See also saline soil, saline-sodic soil, and sodic soil.


Sand

Soil particles between 0.05 mm and 2 mm (in some countries 0.06 mm is the lower size limit), with low specific area and also used as a texture class name for coarse soil materials. Unlike clays, sandy soils do not shrink and swell on drying and wetting and, unless artificially compacted, are rapidly permeable.


Secondary mineral

A mineral resulting from the decomposition of a primary mineral or from the reprecipitation of the products of decomposition of a primary mineral. Silt: Soil particles between 0.002 mm and 0.05 mm (in some countries 0.06 mm is the upper size limit), with high or medium-high specific area influencing stability of soil structure; also used as a texture class name for medium and medium-fine soil materials.


Silt

Soil particles between 0.002 mm and 0.05 mm (in some countries 0.06 mm is the upper size limit), with high or medium-high specific area influencing stability of soil structure; also used as a texture class name for medium and medium-fine soil materials.


Sodic soil

Soil with excess of sodium, pH is higher than 7, usually in the range 8 - 10, exchangeable sodium percentage, ESP> 15 and very poor soil structure. These soils need special management and are not used for agriculture; non-sodic soils are without excess of sodium.


Soil biology

A scientific discipline dealing with living components of soils, which are represented mainly by bacteria, fungi, protozoa, nematodes, arthropods and earthworms as well as by mammals.


Soil chemistry

A scientific discipline dealing with chemical properties of soils and studies on the influence of fertilizers, pesticides and the other chemical substances applied on or into the soil on soil behaviour and fertility.


Soil classification

Also termed soil taxonomy, is the scientific discipline dealing with grouping of soils into soil morphological units or soil types, according to similar or comparable soil forming properties. Many countries in the world have national soil classification systems but those of FAO, WRB and USDA are used internationally. For transnational comparisons, an international soil classification system, into which the majority of national systems can be translated, is needed. In future, this will be the WRB.


Soil colour

Soil colour is one of the indicators of soil status and depends on many factors, mainly on the amount and state of organic matter and iron oxide, as well as amount of air and water in soil pores; In general, dark soils have high organic matter content, grey soils are waterlogged or anaerobic, brown soils are well-drained and aerated soils. Soil colour is measured using Munsell Soil Color charts.



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