Potassium in Your Aquaponics System
Potassium is almost always deficient in mature aquaponic systems unless it is supplemented. Plants, and especially flowering and fruiting plants, consume potassium at rates significantly higher than rates of input. This basically means that in order to have healthy plants, you’ll have to artificially bump up the amount of potassium in your system. Miss part 1? Read the Introduction to Potassium here.
Supplementing Potassium in Your System
You can do this one of two ways- by adding potassium to your system solution, or by applying it foliarly (spraying it on the plant leaves). Adding potassium to your solution is often the easiest way to supplement potassium, but it can also be problematic. This is because the amount of potassium you add to your system isn’t always what is available to your plants. Potassium is being consumed by other organisms in the system and is often reacting or interacting with other elements in ways that we don’t expect. This means that our plants can show potassium deficiency symptoms, even if there is technically plenty of potassium in the system.
Potassium’s Relationship Status: “It’s Complicated”
Potassium has a complicated relationship with other elements- namely Calcium and Magnesium (both very important nutrients in their own right!).
Calcium is the primary nutrient that complicates potassium in many systems. It is very common in aquaponic systems to use calcium carbonate to “buffer” pH, and even where it isn’t common, there are many areas where water is hard with calcium based carbonates. This means that calcium is entering the system in the form of fish feed as well as calcium carbonate. While calcium can be deficient in many systems, there are a few where it is abundant to the point that it impacts potassium availability. This means that when there is lots of calcium present, it can reduce a plants ability to take up enough potassium, leading to deficiencies. The same is also true of magnesium, but to a lesser extent.
Seek a Balanced Aquaponics System
So, it is important to maintain a balance between these three contenders if you wish to supplement potassium effectively. We must make sure that we are not supplementing one at the expense of the others. There are two ways to accomplish this:
- Balancing inputs (maintaining a balance between Potassium, Calcium and Magnesium additions based on your system’s needs)
- Applying one, or all of these nutrients foliarly (essentially bypassing much of the issues with trying to balance nutrients in solution).