Phosphorus circulates though water,the earth's crust,and living organism in the phosphorus cycle, depicted in figure 3-5. In contrast to the cycles of water,carbon,and nitrogen,the phosphorus cycle does not include the atmosphere.The major reservoir for phosphorous is phophate salts containing phosphate ions in terrestrial rock formation and ocean bottom sediments.The phosphorus cycle is also slow compared to the water,carbon,and nitrogen cycles.