Phosphorus (P) is present in every living cell, both plant and animal. No other nutrient can be substituted for it when it is lacking.
Phosphorus is one of the 17 essential nutrients that plants need for growth and reproduction, and is considered one of the three major nutrients along with nitrogen (N) and potassium (K). They are termed major nutrients because of the relatively large amounts utilized by plants (Table 1) and the frequency with which their deficiencies limit plant growth.
Phosphorus must be added to the soil when the native supply is too low to support healthy crop growth. Maintaining an adequate supply of phosphorus is essential for plant health and high yields.
Phosphorus in Plants
Phosphorus is a vital component in the process of plants converting the sun’s energy into food, fiber and oil. Phosphorus plays a key role in photosynthesis, the metabolism of sugars, energy storage and transfer, cell division, cell enlargement and transfer of genetic information.
Phosphorus promotes healthy root growth, promotes early shoot growth, speeds ground cover for erosion protection, enhances the quality of fruit, vegetable and grain crops, and is vital to seed formation.
Adequate phosphorus increases plant water use efficiency, improves the efficiency of other nutrients such as nitrogen, contributes to disease resistance in some plants, helps plants cope with cold temperatures and moisture stress, hastens plant maturity and protects the environment through better plant growth.
Phosphorus in Soils
Plant roots can only acquire phosphorus from the soil when it is dissolved in soil water. Since only very low concentrations of phosphorus are present in the soil water, it must be continually replenished from soil minerals and organic matter to replace the phosphorus taken up by plants.
Phosphorus present in soil organic matter is not available for plant uptake until soil microbes convert the organic compounds into simple inorganic phosphate. Plant roots generally absorb phosphorus as inorganic orthophosphate ions (HPO42– or H2PO4– ).
Many soil factors affect phosphorus availability to plants, including the type and amount of clay minerals, phosphorus concentration, factors affecting root activity (such as aeration and compaction), soil moisture content, temperature, adequate supply of other essential plant nutrients, and the root properties of the crop. Additionally, soil pH (acid or alkaline) greatly influences the availability of phosphorus to plants (Figure 1).
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Fertilizing Soils With Phosphorus
Very few soils contain an adequate supply of all of the mineral nutrients required for unrestricted crop growth. Soil and plant analysis can be used to assess the need for additional phosphorus fertilizer.
Careful nutrient management should accompany the use of all plant nutrients, including phosphorus. Without proper management, excessively high phosphorus concentrations can sometimes lead to unwanted nutrient loss.
Phosphorus Deficiency Symptoms
The first indication of a phosphorus shortage is often a stunted plant, which is difficult to diagnose. Leaf shapes may be distorted.
With severe deficiency, dead areas may develop on leaves, fruit and stems. Older leaves are affected before younger ones because of phosphorus redistribution within the plant. Some plants, such as corn, may display a purple or reddish color on the lower leaves and stems when phosphorus is low. (Figure 2).
Summary
Key points to remember before starting any fertilization program include:
- Phosphorus and Potassium positively influence alfalfa yield and stand persistence
- Alfalfa requires balanced nutrition for high yield and persistence. Split applications of phosphorus after the first and last harvests enhance productivity and avoid luxury consumption.
- Broadcast applications of phosphorus fertilizer work well since fine roots are abundant near the soil surface
- Fertilize for high yield. Do not worry about forage quality. Higher yields will compensate for slight reductions in forage quality.
- Do not over-apply potassium and other nutrients since plants can engage in luxury consumption
Phosphorus fertilization increases yields and farmer profits in many soils around the Intermountain West. Apply generously, but stay within your nutrient plan for each field. For more help with the primary nutrient of phosphorus please contact your local IFA Crop Advisor.
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Written by Brett Harman, CCA, and originally published in the IFA Cooperator magazine (vol. 83, no. 2) Summer 2017. Brett is a Certified Crop Advisor (CCA) with IFA Agronomy.
FAQs
Phosphorus plays a key role in photosynthesis, the metabolism of sugars, energy storage and transfer, cell division, cell enlargement and transfer of genetic information.
How does phosphorus affect plant growth? ›
Phosphorus is an essential component of nucleic acids, phospholipids, and energy-rich phosphate compounds, thus, it plays crucial role in root growth, fruit and seed development, and disease resistance. Phosphorus deficiency can stunt plant growth and reduce yield and quality.
Are phosphorus and nitrogen required for plant growth? ›
Nitrogen and phosphorous are critical determinants of plant growth and productivity, and both plant growth and root morphology are important parameters for evaluating the effects of supplied nutrients.
What is the role of phosphorus in plants and animals? ›
Phosphorus is an essential nutrient for animals and plants. It plays a critical role in cell development and is a key component of molecules that store energy, such as ATP (adenosine triphosphate), DNA and lipids (fats and oils). Insufficient phosphorus in the soil can result in a decreased crop yield.
How are nitrogen and phosphorus important in cellular structure and function? ›
Nitrogen and P both underpin photosynthetic processes, cell growth, metabolism, and protein synthesis (Chapin et al., 2011), but their natural sources and rates of supply are very different: in principle, N availability is unlimited as an atmospheric gas, whereas P comes from rock phosphate, renewed with the uplift of ...
What is the major role of phosphorus in plant growth and productivity? ›
Phosphorus is a vital component in the process of plants converting the sun's energy into food, fiber and oil. Phosphorus plays a key role in photosynthesis, the metabolism of sugars, energy storage and transfer, cell division, cell enlargement and transfer of genetic information.
What happens if a plant has too little phosphorus? ›
Phosphorus deficiency commonly causes older leaves to curl, distort, and remain smaller than normal. Unusually purple leaf veins and tip dieback from phosphorus deficiency. Purpling of leaf undersides due to phosphorus deficiency.
Can plants grow without phosphorus? ›
Phosphorus is present in plant and animal cells and is vital to all plants for harvesting the sun's energy and converting it into growth and reproduction.
What is a good source of phosphorus for plants? ›
Chicken and horse manure, bone meal, fish emulsion and rock phosphate are all good sources of phosphorus for plants. Fertilizers with a higher second number, such as 10-20-5, act quickly to boost phosphorus for plants.
What are the symptoms of phosphorus deficiency? ›
Symptoms of phosphorus deficiency include loss of appetite, anxiety, bone pain, fragile bones, stiff joints, fatigue, irregular breathing, irritability, numbness, weakness, and weight change. In children, decreased growth and poor bone and tooth development may occur.
What is the fastest way to add phosphorus to soil? If your plant is in desperate need of a phosphorus boost, start with a regular schedule of foliar kelp fertilizer. At the same time, add a rapid release phosphorous fertilizer to the soil, like bone meal or fish meal.
What are the four functions of phosphorus in plants? ›
Phosphorus (P) is vital to plant growth and is found in every living plant cell. It is involved in several key plant functions, including energy transfer, photosynthesis, transformation of sugars and starches, nutrient movement within the plant and transfer of genetic characteristics from one generation to the next.
What plants need high phosphorus levels? ›
Legume crops, fruit trees, and lettuce need higher phosphorus levels and often benefit from phosphorus-rich fertilizers. By contrast, most houseplants only need high-phosphorus fertilizer if the soil is deficient.
What chemicals help plants grow faster? ›
Fertilizers provide crops with nutrients like potassium, phosphorus, and nitrogen, which allow crops to grow bigger, faster, and to produce more food. Nitrogen in particular is an essential nutrient for the growth of every organism on Earth.
Does phosphorus promote root growth? ›
Phosphorus is, therefore, important in cell division and development of new tissue. Phosphorus is also associated with complex energy transformations in the plant. Adding phosphorus to soil low in available phosphorus promotes root growth and winter hardiness, stimulates tillering, and often hastens maturity.
Why is phosphorus important to plants? ›
Phosphorus is one of the major plant nutrients in the soil. It is a constituent of plant cells, essential for cell division and development of the growing tip of the plant. For this reason it is vital for seedlings and young plants.
What happens if a plant has too much phosphorus? ›
High phosphorus can cause deficiencies in zinc and iron in the soil, as they quickly become unavailable for use by the plants. These micronutrient deficiencies often present themselves by yellowing and withering of the garden plants.
