Phosphorus is one of the most powerful nutrients out of the seventeen key nutrients identified as essential for plants. Excessive amounts of phosphorus can lead to toxicity, whereas its deficiency can impact growth. – Gro Indoor
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Effects of Phosphorus on Plant Health

by 09 Apr 2023

Effects of Phosphorus on Plant Health

In its developmental stages, the human body requires many nutrients obtained from various food sources to grow. The only source of nutrients for humans is their food, including meat, vegetables, and minerals. Food plays an essential role in developing the human body and contributes to health and well-being.

Every nutrient has its effect and role in the human body. We eat food that comes from plants. We can get a good quality of vegetables and food if the plants are in healthy condition and are free from diseases.

Plants require nutrients and minerals that can promote their growth and keep diseases at bay. Seventeen essential nutrients play a vital role in a plant's growth. One of the vital nutrients is phosphorus. Unlike humans, plants rely on the fertilizers that we use for their development. Plants get their nutrition from soil and water.

We all have heard that photosynthesis is indispensable when it comes to plant growth. The byproduct of photosynthesis, i.e., Glucose, Carbon dioxide, and water, results from the breakdown of those seventeen essential nutrients. Phosphorus is one of the significant components of ATP, commonly known as the "energy unit of photosynthesis".

After nitrogen, phosphorus is the second-most substantial nutrient for the plant. It catalyzes the conversion of many biochemical reactions in plants. If a plant is deficient in phosphorus, it will fetch it from other plants having phosphorus, making it a mobile nutrient. Fertilizers and soil amendments rely on three micronutrients that assist in the plant's growth. One of those three micronutrients is phosphorus. Its absence can impact the overall health of a plant, leaving a significant impact on its growth.

Importance of Phosphorous in Plants

Phosphorous is vital for plants and humans alike. It is the substantial component of their DNA, also known as the genetic "memory unit" of every living being. The energy unit ATP is simultaneously essential for human beings and plants. It is also a vital RNA component responsible for reading the genetic code to build proteins and other essential plant growth components. It is in abundant quantities in root tips, growing shoots, and vascular tissues.

Plants cannot survive for long if they have tender stems making them prone to harsh weather and other undesirable conditions. Phosphorous is a crucial element in root development, plant cell activities, and vigorous plant growth. It also contributes to germination processes and bloom production in plants. The nucleic acids in plants refer to their DNA and RNAs regulating their overall growth and other aspects.

Phosphorous is part of a plant's nucleic acids, and it is beneficial for stalk and stem strength. It plays a significant role in root development, making it mandatory to grow root vegetables in specific. As a plant matures, phosphorus changes. In the initial progressive stages, it stimulates root development, regulates photosynthesis by providing energy, and promotes crop maturity at the right time. If your plant lacks phosphorus, the growth and maturity pace of your plant will slow down. The lack of phosphorus also affects the seed-bearing quality of plants' production of fruits and flowers. Plants with adequate amounts of phosphorous can combat diseases more quickly than those deficient in phosphorous.

How can Plants Obtain Phosphorous?

The use of phosphorous has a long history of human consumption and use. It is a naturally occurring compound, and some resources entail its commercial production. Plants can obtain phosphorus from several sources. The nutritional value of each resource can vary. Before you opt for a phosphorous resource, it is vital to understand the kind of phosphorus suitable for your plants. Phosphorous has different types. Each type has different nutritional properties that might not suit your plant. Bone meal can provide up to 27% phosphorous subjected to change depending on decomposition rate, age, and fertilizer application.

Another critical factor that regulates phosphorus availability is the exposure of your plant to the sun, water, soil type, and microorganisms present in the soil. These factors can impact the quality of a plant to extract phosphorus from the soil. The commonly known phosphorus sources are crab and shrimp waste, bone meal, bat guano, crab meal and phosphate rocks.

Bone Meal

Bone meal is one of the most readily available and affordable phosphorus sources. It is an organic amendment that seeps slowly into the soil. The slow seepage allows the phosphorus to be released for up to four months after its first use. It is best suited for those intending to use high-nitrogen amendments to the soil, like manures, to neutralize the soil's nutrients.

Crab Meal

Commonly known as shellfish fertilizer, crab and shrimp waste is another effective garden fertilization option with phosphorus. Crab meal usually involves the shells of crabs and shrimps, but it can also include other kinds of processing waste. It is vital to remember that crab meal has high nitrogen concentrations. They often have mixed wood shavings or barks to neutralize the potency, allowing them to compost for several months.

Besides having high nitrogen concentrations, crab meal contains phosphorous, magnesium, and calcium, making it a great all-purpose nutrient. Such fertilizers are hard to get, but they are essential in enhancing soil fertility and microbial properties. A few crab meal mixtures have high potassium content in them.

Phosphate rocks

The term phosphate rock refers to a combination of phosphorus and calcium. It is available and mined globally, having a slight change in each chemical mixture's chemical composition. Before using fertilizers, it is vital to understand the soil's pH value as phosphate rocks are alkaline.

If your soil's pH is 7, then using an alkaline fertilizer will affect the growth, meaning that phosphate rocks are not for you. It is indeed a popular phosphorous resource due to its cost-effectiveness. It also contains other nutrients like calcium and magnesium that can be beneficial for your plants.

Bat Guano

It is best when used as an amendment dug around the plant or watered as tea. It offers high phosphorus content. Its organic synthesis makes it a go-to option for organic growers, but it can be expensive for cost-effective fertilizers.

Get to Know What's in the Soil

Humans go through multiple diagnostic tests to rule out what is deficient in their bodies. Similarly, testing your plant growing medium is essential to know what nutrients it lacks to avoid overfeeding. Plants that do not have fruits or flowers do not require much phosphorus, like grass and other grass-like plants.

In case you have overfed your plant with phosphorus, the plant leaves will be the indicator to let you know about the overfeeding. The leaves become spotted and start to appear dead looking when there is an excess of phosphorus.

On the other hand, phosphorus deficiency in soil can also affect the accessibility of zinc and copper content.

In such a scenario, the only reason you can get to know about phosphorus deficiency is to notice the zinc and copper deficiency. When a plant lacks an adequate amount of zinc and copper, it shows symptoms like chlorosis, decreased yields, and dark, twisted leaves.

Understanding Phosphorus Toxicity

Anything that exceeds the standard limit required by a living being; leads to that particular compound's toxicity. You will rarely find phosphorus overfeeding, but when it happens, it can cause various issues.

Excessive amounts of phosphorus in the soil affect the microbial activities, mainly of mycorrhizal fungi. These fungi share a symbiotic relationship with plants essential for their health and growth, but this relationship can go awry in the presence of too much phosphorus.

Steps to Overcome Excessive Phosphorus

If excessive phosphorus is added to your plants, you can neutralize the potency by taking the following steps to save your plants.

  • Avoid using more phosphorus.
  • Use a flushing agent or use three gallons of water per gallon of growing media.
  • In the case of hydroponics systems, drain- off some quantities of phosphorus-rich water.
  • Replace the phosphorus-rich water with pure water having a pH range of 6.0-6.7 to restore balance.
  • You can start again after you get rid of the excessive phosphorus from your plants.

Signs of Phosphorus Deficiency

If a plant is growing stunt with leaf colors varying from fresh green to dull green, it probably lacks phosphorus. The stunted growth of a plant results from both nitrogen and phosphorus deficiency. When a plant does not have sufficient phosphorus, the leaf stem or petiole appears bluish or purplish along with its veins.

The phosphorus deficiency targets the old leaves first and gradually moves upwards to the new leaves. The plants yielding flowers or fruits will still do the same, but the size will be smaller and fewer in number due to phosphorus deficiency. In severe deficiency cases, the leaves start to curl downwards and become necrotic, causing them to die off. Other symptoms pointing to phosphorus deficiency are:

  • Stunted plant and leaf growth
  • Dark green or dark purplish leaves sometimes stem as well.
  • Undersized root growth.
  • Brittle and hard stems
  • Spotty leaves
  • Downward curled leaves

Measures to Treat Phosphorus Deficiency

Phosphorus deficiency affects plant growth and makes it susceptible to diseases. Like there is a solution to overcome excessive phosphorus, compensating for the deficiency is also possible.

You can treat phosphorus deficiency by providing cold conditions and adding more iron to the growing medium. The pH of soil plays a vital role in this regard. A pH imbalance blocks the nutrients' uptake from the soil through roots. Alleviating the inappropriate pH range and regularly checking it can reduce soil and hydroponic systems' deficiency. When it comes to preserving the right pH, the plants growing in the soil absorb the nutrients best at 5.5-5.6. In the hydroponics system, the pH range of 5.2-8.6 is best suited for nutrient absorption. In these ranges of pH, the nutrients are easily accessible for absorption.

When the pH is outside these ranges, and phosphorus is available, the imbalance in pH makes it problematic for the roots to absorb sufficient nutrients. Are you willing to know and understand more about the pH of your growing medium? Check out our guides on the relationship between pH and nutrients to provide detailed insight.

Phosphorus Rich Supplements

You have gotten rid of extra phosphorus, maintained the pH, and still facing phosphorus deficiency. It can be a sign of a deficiency of phosphorus in the fertilizer. To compensate for that loss, use the following phosphorus-rich fertilizers:

How to Spot Phosphorus-Rich Fertilizers?

Are you confused between many fertilizers and are skeptical about the sufficient amount of phosphorus? The way to differentiate a phosphorus-rich fertilizer is to look for the NPK numbers. Using compost tea combined with regular feeding fertilizer containing an adequate amount of phosphorus is suitable for plant growth. If you still have uncertainties, you can refer to material safety data sheets (MSDS) to determine fertilizers composition.


Understanding and identifying the excessive and low amounts of phosphorus can be tricky for many growers. Often, you will find out about phosphorus deficiency through their stunted growth. This sign of stunted growth can be difficult to differentiate as it can stem from many other botanical issues. It is sensible to test your soil to know about its ingredients in abundance and those going scarce. Read our nutrient deficiency series at to understand the impact of nutrients on plants' health.

Sep 11th 2022
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