“Soil .... is the collection of natural bodies on the earth’s surface, containing living matter, and supporting or capable of supporting plants. At its upper limits is air or water. At its lateral margins it grades to deep water or to barren areas of rock, ice, salt, or shifting desert sand dunes. Its lower limit is perhaps the most difficult to define. Soil includes all horizons differing from the underlying rock material as a result of interactions between climate, living organisms, parent materials and relief. Thus, in the few places where it contains horizons impermeable to roots, soil is deeper than plant rooting. More commonly soil grades at its lower margin to hard rock or to earthy materials essentially devoid of roots. The lower limit of soil therefore is normally the lower limit of the common rooting of the native perennial plants, a diffuse boundary that is shallow in deserts and tundra and deep in the humid Tropics.”
KeywordsZircon Silicate Zeolite Boron Sandstone
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