The foundation of relative dating is it does not have an atmospheric reservoir. The phosphorus cycle does not include gas phase. Its largest reservoir is located in sedimentary rocks, and the cycle begins there. Phosphate from rocks are eliminated and then released into the soil and water. The phosphate ions then absorbed by plants and transferred to animals or organisms which eat plants. It is then returned to the soil by way of excretion and decomposed by plants and animals when they die.