The Primary Nutrients & Plant Growth - Phosphorus' Role


Normal plant growth cannot be achieved without phosphorus. It is a constituent of nucleic acids, phospholipids, the co-enzymes DNA and NADP, and most importantly, ATP.

Phosphorus activates co-enzymes for amino acid production that is used in protein synthesis; it decomposes carbohydrates produced in photosynthesis; and it is involved in many other metabolic processes required for normal growth, such as photosynthesis, glycolysis, respiration, and fatty acid synthesis. It enhances seed germination and early growth, stimulates blooming, enhances bud set, aids in seed formation, hastens maturity and provides winter hardiness to crops. The meristem region of growing plants is high in phosphorus. The phosphorus content in Indian soils ranges from low to medium. The highest levels are found in soils where vegetable crops have been grown. High concentrations are also found in fields where heavy rates of poultry litter have been applied.

Plants with phosphorus deficiency are characterized by stunted growth, dark green leaves with a leathery texture, and reddish purple leaf tips and margins. Reddish purple margins are typical of phosphorus deficiency for corn. Symptoms usually occur on young plants when the soil temperature is below 150C. Deficiency symptoms may appear when the soil's phosphorus levels are adequate. When soil is cool, less phosphorus is available for plant uptake, whether or not an adequate amount is present. Symptoms related to cool weather generally disappear as soil temperature increases. Some corn growers apply a starter fertilizer containing phosphorus to offset the effects of cool weather during early season growth.

Deficiency of phosphorus is rarely observed when the soil temperature is above 150C. Warm-season crops are more likely to show early season deficiency symptoms than cool-season crops. Bud set of some ornamental and fruit crops are dramatically reduced by low phosphorus. Usually if soils are high in phosphorus, then rates of application have exceeded crop requirements over the years. Since phosphorus does not leach in mineral soils, any problems associated with surface water contamination can be attributed to soil erosion.

The symptoms of Phosphorus deficiency generally occur in soils with low phosphorus content. An application of phosphate fertilizer based on rates recommended by a soil test will correct this problem. Phosphorus occurs in organic fertilizers (manures); inorganic blended fertilizers; and high phosphate materials such as mono-and di-ammonium phosphate (11-48-0   18-46-0), triple superphosphate (0-46-0), and liquid mixes such as 10-34-0.