Abstract
Typical noncrystalline and poorly crystalline materials in soils are allophane, imogolite, ferrihydrite and humus. These materials occur in Andisols and spodic horizons in relatively high amounts. The humus is complexed with Al in these soils and the humus-Al complex shows high resistance to decomposition. Chemical characteristics of the soils with these materials are variable charge, high phosphate fixation and so on. The variable charge sites show high preference to multivalent cations. Although silicon and some alkaline and alkaline-earth elements are removed, many heavy metals are retained in Andisols during formation of the Al and Fe-rich variable charge materials. These characteristics were problems for crop production but they were mostly amended by high input of fertilizers. Physical characteristics of the soils with these inorganic and organic materials stem from stable aggregates and porous structure, leading to low bulk density, high water retention, high water and air permeability. These physical characteristics are suitable for upland crop production. Allophane and imogolite are natural nano-porous materials expected also for industrial uses such as humidity control, dewing control and heat exchange at the temperature lower than 373 K.
