Organics Skeletal Matter

The amount of organic matter in skeletal material can be as low as 0.01 percent in some mollusc shells, and as high as 20 to 30 percent in vertebrate bones or teeth in a few isolated instances concentrations may go up to 90 percent. The origin, nature and function of mineralized tissues in calcification is only tentatively known. 

Potassium is bound rapidly in silicates and adsorbed in day minerals, albeit very loosely in soil organic matter. Most agricultural soils continue to supply potassium for a long time (> 20 years). Potassium appears to be plentiful in most forest soils, but exceptions are add glacial outwash sands, soils vdth a low clay content and skeletal soils, for example, derived from quartzit. Subsoils are almost always low in exchangeable potassium. 

A major proportion of the organic matter on Earth is plant tissue ( biomass ) and is composed of carbohydrates, principally cellulose. This is the structural support polymer of land plants and the material used since ancient times in the form of cotton and linen textiles, and later as paper. Chitin is a polymer related to cellulose that has skeletal function in arthropods and fungi. Other polymeric carbohydrates constitute the structural support framework for marine plants and the cell walls of microorganisms. The sweet carbohydrate of sugar cane, now termed sucrose, has been a dietary item for at least 10 millennia. 

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