- Phosphorus deficiency is more pronounced in young plants, but the symptoms shown by them persist to maturity.
- Phosphorus has no mobility in the soil, nor does it leach out. Therefore, it should be applied in the root zone. But it has mobility in the plant.
- It is used by young seedlings after germination till they develop roots and start absorbing Phosphorus from the soil.
- In case of Tomato, Cabbage, Sweet Corn, etc., the carbohydrates accumulated in Phosphorus deficient plants are not released by Phosphorus for plant growth. The scanty Phosphorus supply may not have any negative effect on the formation of sugars, which may be abnormally large. In this case, the purple coloured pigment in plant – the Anthocyanin – dominates over green coloured pigment – the Chlorophyll. Thus the leaves of Phosphorus deficient plants exhibit purple colour.
- It exhibits synergism with Nitrogen. Similarly, increased uptake of Phosphorus initially increases the uptake of Calcium, Zinc, Copper and Molybdenum. But very heavy doses of Phosphorus induce Zinc deficiency.
- Phosphorus requirement is more in case of fruit crops.
- Phosphorus is a constituent of nucleoproteins, phytin and lecithin. Phytin is an important Phosphorus constituent in seeds.
- It plays a crucial role in seed germination, root formation and formation of new cells.
- It helps in cambial activities.
- Adequate quantity of Phosphorus is required for starch deposition in seeds, grains, tubers and other storage organs of plants. It hastens maturity in plants.
- It is also required for converting sugars to celluloses, which in turn act as building blocks for a cell.
- Phosphorus is a part of ADP and ATP. Both of them serve as the energy currency for various processes in the plant.
- It helps to overcome harsh winter conditions and increases water use efficiency in crops.
GENERAL DEFICIENCY SYMPTOMS
- Inadequate supply of Phosphorus reduces the number as well as efficiency of nodule bacteria.
- Deficiency of Phosphorus leads to poor germination, poor root and seedling development.
- Its deficiency results in dark green or purple violet coloration of the leaves.
- As the rate of cell division slows down due to scanty Phosphorus supply, its deficiency results in stunted plant growth and spindling of roots and tops.