Phosphorus must be physically added to the soil to increase the supply available to plants. Phosphorus cannot be fixed from the atmosphere.
Deficiency symptoms are purple stems and leaves; maturity and growth are retarded. Yields of fruit and flowers are poor. Premature drop of fruits and flowers may often occur. Phosphorus must be applied close to the plant's roots in order for the plant to utilize it. Large applications of phosphorus without adeguate levels of zinc can cause a zinc deficiency.
Functions in plant:
Phosphorus is necessary for seed germination, photosynthesis, protein formation and almost all aspects of growth and metabolism in plants. It is essential for flower and fruit formation.