In the Lensli Academy we regularly inform you about practical situations that we encounter in the sector, we talk about insights gained in practice, we give you cultivation tips and we share our knowledge about other interesting substrate-related matters.
Academy – Potassium
Potassium (K) is an essential mineral for plant health and growth. It plays an important role in the cell structure of plants. It provides strength to the cell walls and helps plants to stand upright. The absorption of potassium by the roots increases when the plant starts to grow generatively. As soon as the plant blooms or starts fruiting, the uptake from substrate will increase sharply.
Potassium in the plant
Potassium is absorbed from the substrate as a K+ ion. It is therefore a monovalent element and easier for the plant to absorb than, for example, calcium or magnesium. This makes dosing potassium an important one. In the past, where we often used highly peaty substrates, a ratio of 4-2-1 (K-Ca-Mg) was usually found due to the interaction of fertilizers and the absorption complex of peat.
Potassium takes care of the following processes in the plant
• Cell structure and firmness
• Protection against drought and frost
• Regulate stomata and thus moisture balance
• Photosynthesis and energy supply
Too low a potassium level can cause yellowing of old leaves or falling needles on conifers. At low values, leaves can also wrinkle and negatively affect their elongation. Too high a potassium level can manifest itself in displacement of calcium and magnesium.
Potassium in substrate
The use of peat substitutes such as compost, coconut and bark creates a different balance in the substrate. These raw materials inherently contain more potassium. We try to take this into account with our advice and substrate production. This is important because we do not want to see an antagonistic effect on Calcium or Magnesium absorption. For example, we have developed an NP fertilizer for substrates where we already add more potassium from the raw materials. Also read more about this on our Academy: NP Fertilizer article .
Since potassium is a main element with many important functions for plant growth, fertilization must of course be added again over time. Always do this after assessing a fertilization analysis. As long as an analysis of the water-soluble portion in the substrate shows that the ratio is somewhere around 4-2-1 and 2-2-1, a deficiency should not occur quickly. Some raw materials in substrate can also bind potassium strongly, such as garden peat or clay. Coconut products also have a strong bond with potassium. The coconut complex is largely occupied with potassium and sodium, where an exchange with more calcium has taken place after buffering. This is taken into account, for example, with the PG-Mix or coated fertilizers. If there is a higher need towards the end of the cultivation, various High Potassium formulas are available among the slow-release coated fertilizers (CRFs).
More information?
Consult with your Lensli advisor to optimally fertilize the substrate for your own situation.
Do you have questions or would you like to know more about this subject? Please contact your Lensli account manager or product manager. You can also reach us via info@lensli.com and +31 (0)88 22 44 800.
Our team of dedicated, enthusiastic specialists is happy to help!
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