Question

How does fertilizer affect the phosphorus cycle?

Answer 1

Hint: The chemical fertilizer that is used mainly has nitrogen, phosphorus and potassium (NPK). Whenever harmful chemicals seep through the soil it leads to contamination of the soil and ground water and also affects various biogeochemical cycles.

Complete answer:
This answer consists of 2 parts- phosphorus cycle and how fertilizers affect it:
Phosphorus cycle-
• During rainfall or weathering of rocks inorganic phosphates seeps from the weathered rocks and percolates to the soil. This inorganic phosphate is taken up by plants by absorption.
• Animals eat plant or plant products and thus inorganic phosphate gets incorporated into their biological molecule i.e., DNA.
• When a plant or animal dies the inorganic phosphates are again returned to soil. This inorganic phosphate also enters the water bodies and ends up again in the sediments and the cycle continues.

Effect of fertilizers on phosphorus cycle-
Fertilizers have both positive and negative effects. Whereas fertilizers replenish the lesser amounts of phosphates available for plants on the contrary, it gets mixed up in soil and when it seeps through it pollutes the groundwater which is consumed by other species and it affects their biological system. Phosphates and nitrates when leached into water leads to growth of algae which depletes the water of oxygen and effects aquatic animals

Note: Whenever phosphorus is supplied to plants in the form of inorganic phosphate it replenishes the soil of lesser phosphates but on the other hand too much phosphorus pollutes the environment and affects terrestrial and aquatic animals. When too much phosphorus starts accumulating it leads to biomagnification. So use of chemical fertilizers must be reduced or avoided.