Common Plant Deficiencies

As much as we wish everything was all smooth sailing as an aquaponics farmer, we unfortunately still come across our daily struggles. Like in any farming practice, it’s important to always check your plants for nutrient deficiencies.

All our recommended treatments for plant deficiencies are 100% safe remedies. This is crucial in an aquaponic system because we cannot add ingredients that could cause harm to the fish or disrupt the balance of the system.

Even though the fish provide a nitrogen source, it is still possible to have a nitrogen deficiency. The telltale signs of this deficiency are the yellowing of the tips and the centre vein of the bottom leaves. However, you can also get a nitrogen toxicity issue if your nitrogen levels are too high. Leaves turn a deep green to a black colour and the fruiting process could be disrupted.

Solution: Make sure your plant to fish ratio is correct. Check out our blog post on stocking density for more info.

Phosphorous deficiencies usually show up in the older leaves of the plant which are usually located at the bottom. So, make sure to check your bottom leaves to see if they are very dark green in colour with red or purple margins. Plants with phosphorous deficiencies are usually smaller plants with a stunted or slow growth rate.

Solution: We like to treat phosphorous deficiencies by adding mineralised waste to the system on a weekly basis. Check out our blog on mineralisation for more information.

Potassium is a regulating chemical that assists in the movement of water in the cells. The first sign of a potassium deficiency is the yellowing of the tips and edges in young leaves.

Solution: Bury banana peels in the media at the base of the plant.

Iron is one of the most common supplemented nutrients in an aquaponics system. The leaves become yellow and have small green veins in older leaves while younger leaves seem to look bleached.

Solution: Check the pH of your system before supplementing. When supplementing in iron, we usually use an iron chelate form. There are three types.

1. FeEDTA – can be slightly toxic so make sure to use it in moderation. This form of iron can only be available to plants if your pH below 6.5. (This is our preferred choice here at Ichthys.)
2. FeDTPA – Only available to plants if the pH is below 7.5.
3. FeEDDHA – This form works well up to a pH of 9 but just note that it does change your water to a red colour.

Magnesium and Iron deficiencies usually go hand in hand. When a plant is lacking in magnesium, the leaves start to lose their colouring in between the veins while the veins remain green. Usually, the older leaves show the first signs of deficiency.

A calcium deficiency tends to appear in the roots, shoots and younger leaves first and causes them to become malformed.

Solution: We like to treat calcium deficiencies by supplementing some calcium nitrate into the system, through the dosing buckets.

Zinc is an immobile micronutrient and this means that the deficiency symptoms will show on the new leaves of the plant. It’s important to note that zinc deficiencies very rarely occur as it is a micronutrient and plants don’t require large amounts of zinc. However, when a plant has a zinc deficiency you will begin to see light discolouration of the leaves between the veins.

Solution: We treat zinc deficiencies by carrying out a foliar application with zinc EDTA applied at a ratio of 1g/litre of water. A great way to prevent a zinc deficiency is to do a foliar spray once a month with Seabrix at 3ml/1 litre of water. This spray contains trace amounts of zinc that should be sufficient for the plants.

Different plants have different sunlight requirements. If plants do not get enough sunlight then the leaves look faded and droopy.

Solution: Try to reposition the plants’ location to ensure they are getting enough light. Also, try to plan out beds and DWCs in the planting stage to ensure all plants are in the optimal position.

When it comes to our plants we like to use the motto of prevention and fast reaction. This is why we spend a lot of our time examining our plants and observing their growth every step of the way. If you can identify a deficiency in the early stages, then you will have a better chance of getting it under control with minimal plant loss. If you are stuck with identifying your plant deficiencies you can download our FREE chart below.