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Assertion: Phosphorus cycle is an imperf...

Assertion: Phosphorus cycle is an imperfect cycle as a sufficient amount of phosphorus combines with `Al^(3+) Fe^(2+)` and `Ca^(2+)` to form insoluble and unavailable salts.
Reason: Phosphate circulation in abiotic environment in lithosphere as well as in atmosphere.

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Phosphorus cycle is an example of sedimentary cycle. Greatest reservoir of phosphate in the world is relatively insoluble ferric and calcium phosphate in rocks. Cyclic pool is soil for terrestrial ecosystems (lithosphere) and water for aquatic ecosystems (hydrosphere). Phosphate circulates in the abiotic environment in lithosphere as well as hydrosphere. Atmosphere or gaseous cycle is absent. Inside soil some phosphorus is lost through leaching. Similarly, a sufficient amount of phosphorus combines with calcium, iron or aluminium and becomes insoluble. It settles and teeth may also remain undergraded. Such phosphorus becomes part of lithosphere. It is released after a very long weathering agencies or are mined. Thus, phosphorus cycle is an imperfect cycle.
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