In phosphorus cycle immobilization, where is phosphate immobilized?

In phosphorus cycle immobilization, where is phosphate immobilized?

• A. Phosphate evaporates into the atmosphere.
• B. Phosphate dissolves in water only.
• C. Phosphate binds to clay surfaces and organic matter, becoming immobilized.
• D. Phosphate forms atmospheric ozone.

Answer: (C)

Immobilization in the phosphorus cycle means phosphate becomes unavailable to plants because it’s held in forms that are not readily exchangeable. In soil, phosphate can bind tightly to clay surfaces and to organic matter, or be taken up by soil microbes and stored in their biomass. These forms are not easily moved into the soil solution, so the phosphorus cannot be easily absorbed by plant roots. That’s why the idea that phosphate binds to clay surfaces and organic matter, becoming immobilized, is the best description. Phosphate doesn’t evaporate into the atmosphere, and while some phosphate may exist dissolved in water, that state isn’t immobilized; it’s more available for movement and uptake until it binds or is mineralized. Phosphate also doesn’t form atmospheric ozone.

Immobilization in the phosphorus cycle means phosphate becomes unavailable to plants because it’s held in forms that are not readily exchangeable. In soil, phosphate can bind tightly to clay surfaces and to organic matter, or be taken up by soil microbes and stored in their biomass. These forms are not easily moved into the soil solution, so the phosphorus cannot be easily absorbed by plant roots. That’s why the idea that phosphate binds to clay surfaces and organic matter, becoming immobilized, is the best description. Phosphate doesn’t evaporate into the atmosphere, and while some phosphate may exist dissolved in water, that state isn’t immobilized; it’s more available for movement and uptake until it binds or is mineralized. Phosphate also doesn’t form atmospheric ozone.