Function and management of potassium in hydroponics
Potassium is recognized as a nutrient that is required for the good quality of our plants and fruits. Due to its function as an enzyme activator, this nutrient has a major influence on many plant processes. Potassium also plays an important role in opening and closing stomata due to its function as an osmotic regulator.
If we go beyond the physiological role of potassium in plant physiology and focus on plant production, we can learn that potassium has an impact on fruit size, appearance, color, soluble solids, acidity, vitamin content, taste, and shelf life. Sounds important right? There is evidence to support the role of potassium in fruit juice content, vitamin C and resistance to degradation during transport and storage. It is therefore important to understand how potassium works in plants and to carefully monitor potassium levels throughout our harvest cycle in hydroponics.
As mentioned above, potassium can have an impact on many variables related to fruit quality. Potassium is involved in the generation phase of all cultures. For example, in flowering, potassium is used to effectively carry out processes such as pollen germination. If the germination of the pollen cannot be successfully completed, this has a direct effect on the flower formation and thus on the yield.
Most of the time, when a crop is ready to grow some flowers, a change in nutrient balance is required. You will usually notice an increase in potassium as you move from the vegetative phase to the generative phase. Plants need more potassium to produce flowers and fruits!
How to use potassium in nutritional recipes
Potassium is a cation and plays a role in cation exchange capacity, which helps protect anion and cation balance and directly affects important variables in root zone management for hydroponic systems such as pH, osmotic pressure and electrical conductivity.
How much potassium is needed in fruit crops and leafy vegetables?
The amount of potassium required by different plants is completely crop specific and can vary between 100 and 300 ppm. In leafy vegetables we can maintain the same potassium level throughout the cycle, but for fruit crops it is necessary to increase the potassium level in the generative phase. Here below is an example of the potassium levels required for various fruit crops and lettuce.
It is important to always keep the potassium levels used in your formula in balance. If the potassium level is higher than the required level, it can affect the absorption of passive nutrients like Ca and Mg and lead to several nutrient deficiencies. If potassium levels are lower than recommended, dry matter in leaves, stems and roots will generally decrease. When growth is impaired, there is less leaf area available for photosynthesis. The absorption of passive nutrients will also increase. The next phase is when roots begin to regulate architecture and look for more potassium, ultimately reducing electron transport and creating toxic molecules that cause chlorosis and necrosis, the most common symptoms of potassium deficiency. Potassium migrates from old leaves to new leaves, causing symptoms to appear in older leaves. Usually necrosis and chlorosis start on the leaf margin.
How potassium is absorbed into the nutrient solution
There are several types of compounds that can be used in the nutrient recipes. The most common sources of potassium are:
- Potassium sulfate
- Potassium nitrate
- Potassium phosphate
- Potassium chloride
Potassium chloride is most often used to increase potassium when deficiencies arise due to the high levels of potassium found in this compound.
Remember to keep your plant nutrition in balance and make the right changes throughout the harvest cycle to get the best quality and production from your crop.