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What Does Potassium Do?

Recently a customer asked me what does potassium do for my plants?  In the rush of the moment, I failed to answer his question adequately, so I am going to try to do better now.

Actually, Potassium, the K listed as the third macro-nutrient on a fertilizer container, never enters the the plant structure.  It works as a catalyst, but is crucial to the survival of the plant because it activates about 60 different enzyme processes.  It changes the physical shape of some molecules so that the appropriate chemical sites are available for reaction.  It also neutralizes some compounds within a plant to stabilize pH.  Some chemical reactions are controlled by the amount of potassium within the cell and the rate that K enters a cell.  It contributes to the exchange of gases, carbon dioxide and oxygen, and water between the air and plant.  It helps in water intake by the roots and water conservation by the leaves.  And it can even change the direction of leaves so that they are better exposed to the sun!

Potassium is an essential catalyst in photosynthesis and the production and transport of sugars, especially ATP, the first energy product of the plant.  It also is important in the transport of water, nitrates, phosphates, calcium, magnesium,  amino acids, and growth hormones.  It is required for the transcription of DNA to produce proteins for photosynthesis and for the synthesis and movement of vital starches to storage organs.

Silica, which is accumulated in larger quantities when potassium is adequate, results in stronger, thicker cell walls creating a barrier to pathogens and thus a reduction in disease. 

Potassium deficiency makes leaves take a blue hue or yellowing between leaf veins and/or scorching of the outside of the leaves that may lead one to think that the plant needs more water. 

Prevention and cure is effected by simply adding this essential potassium or potash (K2CO3) to the soil.  Potash is easily obtained from wood ash which should be used in very small amounts or first composted.  In Panama, another good source is decayed banana peels, comfrey, or other organic fertilizers.  This writer will not recommend inorganic potassium sources.

Please do ask questions if there are points that are unclear.  In the meantime, I wish you Happy Growing.

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