web counter
Login to SMART!

Log In


Author: Mr. Guy Sela, CEO of SMART! Fertilizer Management software and an international expert in plant nutrition and irrigation.


Potassium is an essential plant nutrient and is required in large amounts for proper growth and reproduction of plants. Potassium is considered second only to nitrogen, when it comes to nutrients needed by plants, and is commonly considered as the “quality nutrient.”

It affects the plant shape, size, color, taste and other measurements attributed to healthy produce. 

Plants absorb potassium in its ionic form, K+.


Potassium has many different roles in plants:

    • In Photosynthesis, potassium regulates the opening and closing of stomata, and therefore regulates CO2 uptake.

    • Potassium triggers activation of enzymes and is essential for production of Adenosine Triphosphate (ATP). ATP is an important energy source for many chemical processes taking place in plant issues.

    • Potassium plays a major role in the regulation of water in plants (osmo-regulation). Both uptake of water through plant roots and its loss through the stomata are affected by potassium. 

    • Known to improve drought resistance.
      Protein and starch synthesis in plants require potassium as well. Potassium is essential at almost every step of the protein synthesis. In starch synthesis, the enzyme responsible for the process is activated by potassium.
  • Activation of enzymes – potassium has an important role in the activation of many growth related enzymes in plants.


Potassium deficiency might cause abnormalities in plants, usually the symptoms are growth related.

Potassium defficiency symptoms  

Deficiencia-de-potasio-en-banano.png   Deficiencia-de-potasio-en-naranja.png   Deficiencia-de-potasio-en-papa.png

Potassium deficiency                Potassium deficiency         Potassium deficiency 
           in banana                                  in citrus                             in potato

Cholrosis – scorching of plant leaves, with yellowing of the margins of the leaf. This is one of the first symptoms of Potassium deficiency. Symptoms appear on middle and lower leaves.  

Slow or Stunted growth – as potassium is an important growth catalyst in plants, potassium deficient plants will have slower or stunted growth.

Poor resistance to temperature changes and to drought – Poor potassium uptake will result in less water circulation in the plant. This will make the plant more susceptible to drought and temperature changes.

Defoliation - left unattended, potassium deficiency in plants results in plants losing their leaves sooner than they should. This process might become even faster if the plant is exposed to drought or high temperatures. Leaves turn yellow, then brown and eventually fall off one by one.

Other symptoms of Potassium deficiency:

  •   Poor resistance to pests
  •   Weak and unhealthy roots
  •   Uneven ripening of fruits

Proper fertilizer management can avoid potassium deficiencies and damage to crops.

A database of the potassium requirements of hundreds of crops is available Here.

Continue reading about potassium in soil.



  •   Crop and field-specific fertilizer recommendations
  •   Get higher yields through fertilizer optimization
  •   Easy to use - you can start now