Subcategories


 

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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.

Seepage, percolation

The movement of water through the soil.

Sheath

Tubular structure formed around a chain of cells or around a bundle of filaments. The fine, polysaccharide sheaths formed by some filamentous cyanobacteria help bind soil particles together and can be seen dangling from soil surface fragments. Ectomycorrhizal fungi form a sheath of hyphae around plant roots.

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. (NB: USDA classification uses 0.05 instead of 0.06)

Slake test

A measure of disintegration of soil aggregates when exposed to rapid wetting.

Slaking

Sealing of the (upper few cm) soil by the destruction of soil aggregates after wetting, causing a fine crust to occur, which reduces permeability of the soil and hamper seedling emergence.

Slope

The inclination of the land surface from the horizontal. Percentage of slope is the vertical distance divided by horizontal distance, multiplied by 100. Thus, a slope of 20 percent is a drop of 20 m in 100 m of horizontal distance.

Slurry

A liquid mixture of livestock urine and faeces, with or without some water and or bedding material.

Socio-economic (social economic) science

Field of study that focusses on the relationships between social and economic factors including their interactions.

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.

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