Blog
Importance of Phosphorus in Plants and Types of Phosphorus Fertilizers
Importance of Phosphorus in Plants and Types of Phosphorus Fertilizers
Phosphorus is one of the three primary macronutrients alongside nitrogen and potassium in plant nutrition. While nitrogen is considered the main factor in vegetative growth, phosphorus plays a key role in energy transfer, root growth and development, plant reproduction, and increasing plant resistance.
Phosphorus Management in 30 Seconds
Phosphorus is a major component of compounds such as ATP and directly participates in photosynthesis, respiration, and cell division. Plants mainly absorb phosphorus in the form of phosphate ions H₂PO₄⁻ and HPO₄²⁻, with a soil pH between 6 and 7 being optimal for absorption. Diagnosis is difficult, but dark green older leaves with a purple underside indicate deficiency. Base fertilizer choices on soil tests, avoiding highly fixing practices like surface broadcasting in calcareous soils.
Role of Phosphorus in Plants
Providing phosphorus during the early stages of growth is very important and essential for the development of the root system. Phosphorus deficiency at the beginning of the growing season causes reduced root growth, decreased lateral root development, weak plant establishment, and reduced ability of plants to absorb water and nutrients.
Phosphorus is present in the structure of proteins, fats, and nucleic acids and is essential for the synthesis of DNA and RNA molecules and the genetic structure of plants.
Energy transfer
Phosphorus is a major component of adenosine triphosphate (ATP), known as the energy currency of the cell.
Root system
Providing phosphorus early ensures lateral root development, aiding successful plant establishment.
Reproduction
In the reproductive process, phosphorus plays a role in flowering, formation of reproductive organs, and seed and fruit formation.
Phosphorus Deficiency in Plants
Diagnosing phosphorus deficiency is usually difficult because its symptoms may be minor in the early stages and become clearly visible when correction is somewhat late.
Early minor symptoms
Symptoms may be minor in the early stages and become clearly visible when correction is late.
Older leaf changes
The characteristic sign appears in older leaves, where leaf margins become abnormally dark green.
Purple coloration
The underside of leaves becomes purple, and as deficiency progresses, older leaves generally become purple.
Severe signs
Brown spots appear on leaf margins, and root growth is directly disrupted.
Cold conditions increase phosphorus deficiency, which usually disappears as the weather becomes warmer if sufficient phosphorus exists in the soil.
Phosphorus Removal and Use Efficiency
In intensive and modern agricultural systems on irrigated lands, annual phosphorus removal through harvesting is 20–35 kg per hectare. It has been estimated that phosphorus removal from a wheat field with a yield of 10 tons per hectare is about 40 kg, from a canola field with a yield of 4 tons per hectare is about 30 kg, and from a potato field with an average yield of 70 tons per hectare is about 40 kg per hectare.
High use efficiency
- Canola has suitable phosphorus use efficiency.
- Alfalfa demonstrates good uptake performance.
- Sugar beet is capable of efficient usage.
- Wheat ranks among plants with suitable efficiency.
Poor use efficiency
- Onion struggles with phosphorus absorption.
- Tomato is among the plants with poor efficiency.
- Beans often demonstrate poor use efficiency.
- Most fruit trees fall into this category.
The amount of phosphorus removed from soil does not determine phosphorus requirement; rather, phosphorus use efficiency is important.
Highly Soluble Mineral Phosphorus Sources
Phosphorus fertilizers are divided into two groups based on solubility and absorption rate. The selection depends on soil chemistry, application time relative to planting, application method, and production objectives.
MAP (11-52-0)
Its initial solution reaction is relatively acidic, making MAP a very good choice in many conditions, especially in alkaline soils.
DAP (18-46-0)
Offers the advantage of simultaneous nitrogen and phosphorus supply and is more common than MAP.
TSP (0-46-0)
Highly soluble phosphorus, without nitrogen, suitable for situations where only phosphorus is required.
| Fertilizer type | Characteristics | Application | Key notes |
|---|---|---|---|
| Monoammonium phosphate (MAP) | 11-52-0, highly soluble, acidic reaction. | Pre-planting, fertigation, band application. | Very good choice for alkaline soils; suitable for early growing season in fruit trees. |
| Diammonium phosphate (DAP) | 18-46-0, highly soluble. | Pre-planting. | Proper distance from seeds should be maintained to avoid ammonia damage. |
| Triple super phosphate (TSP) | 0-46-0, highly soluble, without nitrogen. | Pre-planting. | Use in conditions where soil does not need nitrogen but requires phosphorus. |
| Phosphoric acid | Very high phosphorus concentration, corrosive. | Raw material in fertilizer industries or specific fertigation systems. | Can reduce soil acidity for better absorption of micronutrients. |
| Single super phosphate (SSP) | 0-16 or 21-0, contains calcium and sulfur. | Various conditions. | Advantageous if soil simultaneously requires sulfur. |
Slow-release Mineral Sources and Organic Sources
Organic phosphorus can become available to plants directly or after mineralization, but the release rate depends on temperature, moisture, carbon-to-nitrogen ratio, microbial activity, and type of organic matter.
Rock Phosphate
Its total phosphorus may be high, but high phosphorus content does not indicate high availability. It performs better in acidic environments and is not a suitable option in calcareous and alkaline soils.
Organic Fertilizers
This group includes various animal manures such as poultry and cattle manure, vermicompost, plant residues, and some phosphorus-enriched organic fertilizers.
Fixation reduction
Organic compounds can occupy some active sites in the soil, reducing phosphate fixation.
Organic acids
Decomposition of organic matter causes the production of organic acids that play a role in releasing part of the phosphorus.
Microbial support
Organic matter is an energy source for microorganisms that dissolve mineral phosphate and produce organic acids.
Common Mistakes in Phosphorus Fertilizer Application
Avoiding these common mistakes ensures better efficiency without increasing costs unnecessarily.
Ignoring Soil Tests
Annual phosphorus application without soil testing.
Excessive Use
Excessive use of TSP, DAP, or MAP, assuming more phosphorus equals higher yield.
Broadcasting in Calcareous Soil
Broadcasting phosphorus on the soil surface before planting, especially in calcareous soils with high phosphorus fixation capacity.
Humic Acid Overreliance
Applying high amounts of humic acid without phosphorus fertilizers.
Ignoring Zinc
Applying high phosphorus management while ignoring soil zinc levels or not using zinc fertilizers.
Calcium Conflict
Applying phosphorus fertilizers and calcium at the same irrigation time or in the same soil location.
Once the plant's phosphorus requirement is met, applying more phosphorus does not necessarily increase yield.
A Practical Plan for Phosphorus Management
Scientific phosphorus management, especially in soils with limitations in phosphorus supply or uptake, is possible through soil testing, selecting the appropriate source, accurate application at the correct time, and using biological approaches.
Soil testing
Conduct accurate soil testing instead of blind annual applications.
Select an appropriate source
Select the appropriate source based on soil chemistry and production objectives.
Manage soil pH
Consider soil pH, as the best absorption range is between 6 and 7.
Precise application
Ensure accurate application at the correct time and distance from seeds.
Use biological approaches
Use biological approaches with microorganisms producing organic acids.
Integrate organic matter
Incorporate organic matter to improve soil structure and phosphorus mobility.
Phosphorus Management Checklist
Use this checklist before applying fertilizer. Your selections are saved in this browser.
Pre-application field checks
Maximizing Efficiency with Biological Approaches
Biological approaches, such as using microorganisms capable of producing organic acids and releasing fixed soil phosphorus, can increase the availability of phosphorus.
Improve root conditions
Improve root conditions by using organic fertilizers to enhance soil structure.
Support soil microbes
Support soil microbes as organic matter is an energy source for microorganisms.
Leverage organic acids
Leverage organic acids produced by microorganisms to release fixed soil phosphorus.
Lower chemical dependence
Reduce the need for chemical fertilizer application through biological approaches.
Need help selecting the right phosphorus fertilizer?
Send the Kimia Lagon technical team your soil test results, crop type, and field history. A proper recommendation requires exact soil chemistry and pH details—not just a generic application rate.
Final Remarks
Scientific phosphorus management is achievable through rigorous soil testing, selecting the appropriate fertilizer source based on pH, and precise application timing.
Sustainable phosphorus management requires improving efficiency and using alternative resources. Biological approaches can increase the availability of phosphorus present in soil and chemical fertilizers and reduce the need for chemical fertilizer application.
Technical References
The plant nutrition principles summarized in this guide are based on the following document provided for this analysis:
- Phosphorus_in_plants_and_phosphorus_fertilizers_English_translation.docx
Phosphorus Management FAQ
Phosphorus plays a key role in energy transfer, root growth and development, plant reproduction, and increasing plant resistance.
The characteristic sign appears in older leaves, where leaf margins become abnormally dark green and the underside becomes purple.
Generally, the best soil pH range for phosphorus uptake by plants is between 6 and 7.
MAP is relatively acidic and highly suitable for alkaline soils. DAP provides simultaneous nitrogen and phosphorus but can create an alkaline environment and damage germination if placed too close to seeds.
Rock phosphate is not a suitable option for phosphorus supply in calcareous and alkaline soils.
Once the plant's phosphorus requirement is met, applying more phosphorus does not necessarily increase yield.