PHOSPHORUS’S ROLE IN PLANT NUTRITION
symbol: P; available to plants as orthophosphate ions (HPO42-, H2PO4-).
- In photosynthesis and respiration, P plays a major role in energy storage and transfer as ADP and ATP (adenosine di- and triphosphate) and DPN and TPN (di- and triphosphopyridine nucleotide).
- P is part of the RNA and DNA structures, which are the major components of genetic information.
- Seeds have the highest concentration of P in a mature plant, and P is required in large quantities in young cells, such as shoots and root tips, where metabolism is high and cell division is rapid.
- P aids in root development, flower initiation, and seed and fruit development.
- P has been shown to reduce disease incidence in some plants and has been found to improve the quality of certain crops.
Constituent of many proteins, coenzymes, nucleic acids and metabolic
substrates; important in energy transfer
Phosphorus is the second most commonly applied nutrient in most crops and is part of many organic molecules of the cell (deoxyribonucleic acid (DNA), ribonucleic acid (RNA), adenosine triphosphate (ATP) and phospholipids) and is also involved in many metabolic processes in the plant as well as the pathogen.
P has been shown to be most beneficial when it is applied to control seedlings and fungal diseases where vigorous root development permits plants to escape disease.
Phosphate fertilization of wheat can have a significant effect and almost eliminate economic losses from pythium root rot. Similarly, in maize P application can reduce root rot, especially when it is grown on soils deficient in P, and in other studies it can reduce the incidence of soil smut in maize.
A number of other studies have shown that P application can reduce bacterial leaf blight in rice, downy mildew, blue mold, leaf curl virus disease in tobacco, pod and stem blight in soybean, yellow dwarf virus disease in barley, brown stripe disease in sugarcane and blast disease in rice. Foliar application of P can induce local and systemic protection against powdery mildew in cucumber, roses, wine grapes, mango and nectarines.
The phosphorus cycle
It is important to note that Buneba P makes Phosphorous fertilization extremely efficient as it increases soluble phosphorous absortion directly into plant tissue minimizing Phosphorous losses in the environment and reducing significantly Phosphorous requirements in other forms. As such, Buneba P is a truly ecological product, as it contributes to valuable Phosphorous conservation.
Plants absorb P from the soil solution as phosphate in the form HPO– at soil pH below 7.2 and HPO2– at pH above 7.2. Phosphate dissolved in the soil water exists in an equilibrium between P in solution, labile P, and nonlabile P :
Labile P is plant-available P that is adsorbed loosely by the soil but can be desorbed into solution. Nonlabile P has formed stable and relatively insoluble compounds with the soil, and it is not available to plants.
Decomposition of soil minerals through weathering releases P into the soil solution, but the process is gradual. In acid soils, iron and aluminum phosphates are found, while in neutral, calcareous soils, octacalcium phosphate and apatite are found.
Mineralization by microorganisms of P associated with organic matter is important in maintaining levels of P in the soil solution.
Phosphorus is removed in harvested crop materials, but in lesser amounts than nitrogen or potassium. Soil erosion can be a major source of P loss, because P is held tightly by soils. If soil erosion in not controlled, phosphate pollution of the environment can result. Phosphate can be strongly “fixed” (adsorbed) by soils. Under acidic soil conditions, P combines with iron and aluminum. Under neutral or alkaline soil conditions, P combines with calcium.