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Nutrient Deficiencies of Plants in Aquaponics

Producing fresh and organic vegetables is among the major benefits of aquaponics. However, to ensure that your plants are healthy, you need to avoid plant nutrient deficiency in your aquaponic system. Plant nutrient deficiencies are common even in traditional and other farming methods, and it is one of the most common problems in aquaponics

Plant deficiencies in aquaponics occur when essential nutrients are not readily available in fish waste used to feed the plants. Deficiencies can affect plants' growth and make plants more susceptible to plant diseases and insects. In aquaponics, to prevent or treat plant nutrient deficiencies, it is essential to recognize this problem and identify the nutrients that your plant needs.

Tomato with Nutrients Deficiency

Nutrients in Aquaponics

Plants need lights and nutrients to grow. In the traditional method of planting, these nutrients are sourced from the soil. However, in an aquaponic system, these nutrients come from fish waste because of the absence of soil. Nutrients have a significant role in any planting methods. In aquaponics, there are two major categories of nutrients that are essential for the plants in an aquaponics system. 

1. Macronutrients

There are six macronutrients that plants need in large amounts. These nutrients are Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg), and Sulphur (S). Below are the list outlines of the function of these macronutrients within the plants.

  • Nitrogen (N)

Nitrogen is the basis of all proteins and is essential for building structures, photosynthesis, cell growth, metabolic processes, and chlorophyll production. Nitrogen is a key element in aquaponic nutrient solution and serves as a proxy indicator for other nutrients. Usually, dissolved nitrogen is in the form of nitrate, but plants can use small quantities of ammonia and free amino acid to grow. Excessive nitrogen can cause excessive plant growth resulting in lush, soft plants susceptible to diseases and insect damage and difficulty in flowering and fruiting.

  • Phosphorus (P)

Phosphorus is essential for photosynthesis and the formation of oils and sugars, and encourages germination and root development in seedlings. Phosphorus deficiency can cause low root development. 

  • Potassium (K)

Potassium functions as a cell signaling via controlled ion flow through membranes control the stomatic opening and are involved in flower and fruit set. Potassium is involved in producing and transporting sugars, water uptake, disease resistance, and fruit ripening. All plants need potassium and can be affected by low levels of these nutrients.
Potassium deficiency in aquaponic plants needs treatment. Because a lack of potassium can negatively affect photosynthesis, which can also affect plant growth, it can also make the plant susceptible to infection or infestation that could lead to plant death.

  • Calcium (Ca)

Calcium is essential for the plants' healthy growth and sturdy cell walls and helps maintain plants' strength and shape. It is involved in the strengthening of stems and contributes to the production of flowers, fruits, and vegetables. Squash, tomatoes, and peppers are some plants susceptible to calcium deficiency.
It is essential to treat calcium deficiency to prevent ruining the harvestable fruits or vegetables. Low calcium levels can also stunt plant growth and can cause plant death.

  • Magnesium (Mg)

Low magnesium is a common plant deficiency in aquaponics. Magnesium plays a vital role in the plant's internal functions. Magnesium helps in breaking down the chlorophyll. Treating magnesium deficiency is essential to the overall health and growth of the plants.

  • Sulfur (S)

Sulfur is essential for the production of some proteins, chlorophyll, and other photosynthetic enzymes. Sulfur deficiencies are rare in aquaponics.

2. Micronutrients

Micronutrients are iron (Fe), copper (Cu), zinc (Zn), manganese (Mn), boron (B), and molybdenum (Mo). Most micronutrient deficiencies include yellowing of the leaves, but copper deficiencies can darken the leaves into green color.

  • Iron (Fe)

Iron is used in chloroplasts and electron transport chains. Iron is essential for proper photosynthesis. Iron deficiency can be identified easily by using an iron Checker to check the iron level in your water. Another way to identify iron deficiency is by checking if the plants' leaves turn yellow, but the veins remain green, called "choloris." Iron has to be added to the system as "chelated iron." The suggested addition is 5 ml per 1 m2 of grow bed. A large quantity does not harm the system but can cause discoloration of the tank and the pipes.

  • Manganese (Mg)

Manganese is essential to the photosynthesis process of plants because it is used to catalyze water splitting during photosynthesis. Manganese deficiency can be seen by reduced plants' growth rates, a dull grey appearance, and yellowing between veins that remain green.

  • Boron (B)

Boron is involved in the structural polysaccharides and glycoproteins, carbohydrate transport, and regulating some plants' metabolic pathways. Boron is also involved in reproduction and water uptake by cells.

  • Zinc

Zinc is used by enzymes and also in chlorophyll that affects the overall size of the plants.


Interveinal chlorosis caused by iron or nitrogen deficiency on a grape vine with grapes in aquaponics.

Nutrient Sources for Aquaponics

In aquaponics, the primary source of plant nutrients is fish food. However, plants have different nutritional needs than fish, and some other nutrients from the fish waste remain in a solid state that is unavailable for the plants. Fish feed pellets are a complete food for the fish to grow, but not for the plant. Fish do not need the same amount of iron, potassium, or calcium that plants need to thrive. So deficiencies of these nutrients may occur. Below are the common nutrient deficiencies in aquaponics.

Iron Deficiency

Signs of Iron Deficiency:

  • Yellowing color on plant leaves
  • Spots on immature leaves

How to supplement iron:

To supplement iron in your aquaponics system, you need to add iron that the plants can absorb. This means using chelated iron. Adding chelated iron to your system will only be effective if your pH is 7.5 or lower. Your aim is 2 mg/liter, so you need to calculate your water tank's size and add the required amount of iron every 3 - 4 weeks. 

Potassium

Signs of Potassium Deficiency:

  • Older leaves of the plants show interveinal chlorosis and spots or scorching, which progresses to the younger leaves when the deficiency becomes more severe.

    How to supplement potassium:

    • By Spraying - You can use potassium chloride and spray it into the plant leaves. You must repeat the process at least once a week to avoid potassium deficiency in your aquaponics plants.
    •  Adding a potassium supplement to your fish food through kelp meal concentrate. Other options are adding potassium sulfate or potassium hydroxide to your fish food.

      Calcium

      Signs of Calcium Deficiency:

      • Black, dead areas of the young plant tissue, known as necrosis.
      • Slight chlorosis to brown or black scorching on new leaf tips.
      • Fresh leaves are distorted with hooked tips and irregular shapes.

      How to supplement calcium:

      • One way to supplement calcium deficiency in aquaponics is to use hydrated (or agricultural) lime, which will also supplement calcium and magnesium besides raising the pH levels. 
      • Another way is by spraying calcium chloride mixed with some water to your plants. The ratio should be four teaspoons of calcium chloride per gallon of water. You can increase the dose if needed and spray once a week to your plants.

        Phosphorus

        Signs of Phosphorus Deficiency:

        • Stunted plant growth.
        • Darkening of the leaves near the plants' base.
        • Purple or reddish color of the leaves.
        • Spare leaf growth.

        How to supplement phosphorus:

        The most common method to add phosphorus to aquaponics is to use rock phosphate. 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 the direct sunlight to ensure that it doesn't dissolve before the plant can absorb it. 

        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 that plants require to grow by growing media beds. Grow media beds offer an excellent environment for nutrients to develop into 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. 

        Conclusion

        In conclusion, aquaponics is a system that needs to be balanced for the fish, plants, and bacteria to thrive. It is essential to always check the specific water quality parameters and always feed your fish the right food to ensure that your system is a success. Thank you for reading; subscribe to our newsletter for new updates on aquaponics.

         

         

         

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