How to Manage Phosphorus Deficiency in Aquaponics Plants

Phosphorus deficiency is another common nutrient problem that can affect your aquaponics plants. If left unmanaged, it can cause the yellowing of leaves, stunted growth, and even plant death. This article will discuss the symptoms, causes, and ways of adding phosphorus to your aquaponics plants.


Phosphorus Deficiency in Tomato Plants

Why do Plants Need Phosphorus?

Phosphorus (P) is a nutrient essential for plant growth. It is part of the nuclei acid structure of plants responsible for regulating protein synthesis. 

Phosphorus in plants plays an essential role in the growth of new tissues and the division of plant cells. Plants perform complicated energy transmissions that require phosphorus. One benefit of phosphorus is the proper development of plant roots and hastening maturity. Below are the main functions of phosphorus in plant growth:

  • Stimulates root development that is necessary for the plant to absorb the nutrients from the water and give support to the plants. 
  • Boosts plant development. The nutrients absorbed by plant roots are processed in the leaves and stored or transferred to the other parts of the plants. 
  • Phosphorus is required for photosynthesis and storing and transporting nutrients throughout the plant.
  • Phosphorus is responsible for the maturity of the crop at the right time. Plants that lack phosphorus take time to mature, and when they do, they are of poor quality.
  • Phosphorus is required for the development and transfer of plant genes from one generation to the next.
  • Plants with access to enough phosphorus can resist diseases because of their well-developed parts. 

What is Phosphorus Deficiency?

Phosphorus deficiency in plants is not very obvious, but its presence can be shown if plants fail to grow into their normal size or take too long to mature. It can also be visually identified at the early stage on the abnormally dark green, reddish-purple color on the edge of the lower plant leaves or brown or slightly blue splotches or spots on the leaves. These symptoms first appear in the older parts of the plant. Phosphorus deficiency in plants is often seen along with calcium deficiency because these nutrients interact within the plant. 

Signs of Phosphorus Deficiency in Aquaponics Plants

The most common signs of phosphorus deficiency are:

  • Small leaf size
  • Bright red stems
  • Reddish-purple color along the edge of the lower plant leaves
  • Brown or slight splotches or spots on the leaves
  • Shiny leaves with yellow areas
  • Thickening of leaves or leaves becomes dry and stiff

A phosphorus deficiency usually affects the older leaves first, so sometimes the stems are not affected, but there are times that the only sign of the deficiency is the bright red stems.


Leaves with Phosphorus Deficiency

How to Treat Phosphorus Deficiency in Aquaponics Plants

Treating phosphorus deficiency in your aquaponics system requires adding phosphorus to the system to let the plant get the benefits without creating a high phosphorus level in the water. This is because algae like phosphorus, and if the water has a high level of phosphorus, it will develop algae bloom, which is bad for the system. 

Rock phosphate is the most common method of adding phosphorus to aquaponics systems. The supplement can be added directly to your grow beds. Avoid adding it directly to the water, and your grow bed should be shaded from direct sunlight to ensure that it doesn't dissolve before the plant can absorb it. You should aim for around 20 to 40 ppm of phosphorus for your fruiting plants. 

Tips on Supplementing Phosphorus to Your System

  • Use phosphorus or phosphate that comes as powder or granules.
  • Avoid adding phosphorus directly to the water; add it to the grow beds instead.
  • Avoid adding phosphate on plants that do not bear fruits, like leafy greens and herbs
  • Provide extra shading to your system when supplementing phosphate. 

How to Prevent Phosphorus Deficiency in Your Aquaponics System

The best way to ensure that plants will not suffer nutrient deficiencies in aquaponics is to maintain the 6-7 pH water level and feed the fish with a balanced and complete diet. Another good way is to provide all the nutrients plants require to grow by growing media beds. Grow media beds offer an excellent environment for nutrients to develop in your system, and you can also add worms in your grow media bed to help break the solids and provide more nutrients for your plants. 


Plants also needed phosphorus to grow and bear fruits. With phosphorus deficiency, your aquaponics plants will have stunted growth and fail to bear fruit which will also result in the loss of your system. So it is essential to supplement your system with nutrients as soon as you see any deficiency symptoms.

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