Phosphorus Cycle Fertilizers cause irreparably damage to the environment. To understand how fertilizers can drastically change the environment, it is important that we are familiar with the phosphorus cycle. The phosphorus cycle differs from the nitrogen and carbon cycles because phosphorus is unable to achieve the gaseous state in the atmosphere. Phosphorus is mainly found in water, soil and sediments. In the atmosphere, phosphorus is found as fine dust particles. The phosphorous used by plants is predominantly in the form of phosphate salts.  Phosphate salts are released when phosphate rocks are eroded by rainfall, weathering and runoffs. The release of phosphate salts into the soil results in a constant phosphorus supply for plants. Phosphate salts are absorbed through the roots of plants and used to make organic compounds. As animals eat these plants, phosphorus is also consumed and passed up the food chain. The decomposition of these animals or the excretion of organic phosphate returns phosphorus into the soil or water thereby completing the cycle.               In comparison to nitrogen and carbon, the rate at which phosphate salts are released is extremely slow.  Phosphorus can remain in rocks or sediments for millions of years. In addition, the competition between mineralization and immobilization of organic phosphorus helps to delay the amount of phosphates available for use. As a result, the need for plant growth outweighs the amount of phosphate salts being released. To alleviate the phosphate demand, the addition of phosphate fertilizers has become the solution humans employ to maintain and increase crop production. (Part III of Matter Cycles ) Role of Phosphorus in Plant Growth