Where do the Plants get their Nutrients?

Man holding a lettuce seedling for an aquaponics system

Where do the Plants get their Nutrients?

Where do the plants get their Nutrients?

August 26, 2021

It’s common knowledge that a plant’s basic necessities are water, oxygen, sunlight and a good fertilizer. But what happens when we are talking about a soil-less aquaponic system? How does the plant get the required nutrients to survive? Let’s take a closer look at how the plants get their nutrients in aquaponics.

When you buy a bag of fertilizer you will see that there are usually three letters on the packaging. NPK = Nitrogen, Phosphorous and Potassium. These are the main backbones of plant nutrition and are crucial for survival. However, there are still other macronutrients and micronutrients required for optimal plant health.

Plants take up their source of nitrogen in the form of nitrates, and the good news is that these nitrates come as a part of the package in an aquaponics system. The fish waste is converted into nitrates by nitrifying bacteria in the biofilter. The nitrate-rich water is circulated to the grow beds. Ultimately, providing the plants with their nitrate fix.

A lack of any key nutrient will cause a plant deficiency. This occurs in any and every farming technique, and therefore, not subjected to aquaponic farming alone. So, what do we do when something is lacking a nutrient? We supplement it in! It’s recommended that Phosphorous, Potassium, Iron and Calcium are frequently dosed into your system as there are insufficient amounts found naturally in an aquaponic system.

There are two methods of nutrient supplementation that we like to use to make sure that our plants are receiving all their nutrients.

Nutrient supplementation through mineralization

The mineralization process uses what is already given to us in our system: the fish faeces. The fish urine is used in the nitrogen cycle to convert ammonia into nitrates for the plants. But what about the solid waste? Surely, we can utilize the solid waste instead of just throwing it out of our mechanical filter? Well, you can! We can create a mineralized liquid through the process of mineralization, which can be dosed back into our system. Therefore, providing the plants with extra nutrients. To learn more about this process, see our blog post: “Mineralization Explained.”

Tilapia fish in a tank.

Nutrient supplementation through a dosing bucket

A dosing bucket can assist in supplementation. Large quantities of concentrated nutrients can shock the system and cause stress for the fish. Therefore, we highly recommend a dosing bucket. You can add the nutrients daily, weekly or as required. The dosing bucket will gradually release the nutrients into the system. Therefore, avoiding shock and equally sharing the nutrients to the plants without upsetting the delicate balance in an aquaponic system.

Healthy looking plants grown in an aquaponics system

Nutrient supplementation requirements will differ in every system as it’s dependent on the size of your system, the amount of fish, the number of plants and the type of plants you are farming. We know that the plants are definitely receiving enough water but what about dissolved oxygen? It is important to remember that proper aeration needs to be provided to the plants. This is especially crucial in a deep water culture.

You must be constantly aware of your water quality, dissolved oxygen and the levels of nutrients in your system at all times.  We prefer to prevent deficiencies and diseases rather than try and treat a problem that is past recovery. The plants can only take up the nutrients that are available in the system and it is up to you as a farmer to ensure that they have what they need.

Book a course with us today to learn more about aquaponics and caring for your plants as a new farmer.