Chapter 4
Non-crystalline Inorganic Constituents
of Soil
Abstract Non-crystalline inorganic constituents of soil, such as volcanic glasses,
phytoliths, laminar opaline silica, allophane, and imogolite are introduced using
optical and electron microscope images and energy dispersive X-ray (EDX) analysis. The Al-humus complex and Al-rich Sclerotia grains are also introduced. The
volcanic glasses are formed from magma and can be categorized as primary. All of
these non-crystalline inorganic constituents are found in volcanic ash soils. Among
these, phytoliths can be found under vegetation in many other soils than volcanic ash
soils. Formation of allophanic materials from fresh pumice is shown stepwise using
polished sections to demonstrate microscopic distribution of elements and inorganic
constituents. Allophane and imogolite are rich in Al whereas their parent material,
volcanic ash, is silica-rich. Changes in morphological property and element concentration of volcanic ash or volcanic glass during the formation of these secondary
non-crystalline constituents are discussed.
4.1 Introduction
The non-crystalline constituents present in soil depend strongly on soil environmental conditions. The non-crystalline silicate and silica constituents in soil are volcanic
glass, allophane, imogolite, laminar opaline silica, and phytoliths (Table 4.1). All
these are present in volcanic ash soils. Among these materials, allophane and
imogolite are also found in spodic horizons, such as Bs and Bhs horizons, and
they confer unique properties upon Andisols and Spodosols. Volcanic ash soils are
found in volcanic areas worldwide. Spodosols are found mainly in the cold regions
of the world, and can also be formed in volcanic ash deposits. Phytoliths form in
plant cells and occur commonly in many A and buried A horizon soils.
The Al-humus complex is also covered in this chapter despite its partially organic
structure because it is one of the major constituents of active Al. Active Al is
important to the formation of Andisols and Spodosols, classification of these soils,
and the phosphate sorption reaction.
Other non-crystalline materials which may be present in soils include
non-crystalline phases of iron sulfide, iron phosphate, and aluminum phosphate.
© The Author(s) 2018
M. Nanzyo, H. Kanno, Inorganic Constituents in Soil,
https://doi.org/10.1007/978-981-13-1214-4_4
59
Non-crystalline Inorganic Constituents
of Soil
Abstract Non-crystalline inorganic constituents of soil, such as volcanic glasses,
phytoliths, laminar opaline silica, allophane, and imogolite are introduced using
optical and electron microscope images and energy dispersive X-ray (EDX) analysis. The Al-humus complex and Al-rich Sclerotia grains are also introduced. The
volcanic glasses are formed from magma and can be categorized as primary. All of
these non-crystalline inorganic constituents are found in volcanic ash soils. Among
these, phytoliths can be found under vegetation in many other soils than volcanic ash
soils. Formation of allophanic materials from fresh pumice is shown stepwise using
polished sections to demonstrate microscopic distribution of elements and inorganic
constituents. Allophane and imogolite are rich in Al whereas their parent material,
volcanic ash, is silica-rich. Changes in morphological property and element concentration of volcanic ash or volcanic glass during the formation of these secondary
non-crystalline constituents are discussed.
4.1 Introduction
The non-crystalline constituents present in soil depend strongly on soil environmental conditions. The non-crystalline silicate and silica constituents in soil are volcanic
glass, allophane, imogolite, laminar opaline silica, and phytoliths (Table 4.1). All
these are present in volcanic ash soils. Among these materials, allophane and
imogolite are also found in spodic horizons, such as Bs and Bhs horizons, and
they confer unique properties upon Andisols and Spodosols. Volcanic ash soils are
found in volcanic areas worldwide. Spodosols are found mainly in the cold regions
of the world, and can also be formed in volcanic ash deposits. Phytoliths form in
plant cells and occur commonly in many A and buried A horizon soils.
The Al-humus complex is also covered in this chapter despite its partially organic
structure because it is one of the major constituents of active Al. Active Al is
important to the formation of Andisols and Spodosols, classification of these soils,
and the phosphate sorption reaction.
Other non-crystalline materials which may be present in soils include
non-crystalline phases of iron sulfide, iron phosphate, and aluminum phosphate.
© The Author(s) 2018
M. Nanzyo, H. Kanno, Inorganic Constituents in Soil,
https://doi.org/10.1007/978-981-13-1214-4_4
59