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After the nutrient nitrogen, potassium’s share in plant nutrition is the second highest. However, less information about this nutrient is available. First of all, potassium is seen as a mobile element, meaning action is taken by the plant itself once a deficiency is remarked. Secondly, on the contrary to nitrogen being found in the plant’s proteins and enzymes, potassium is not incorporated in the plant.

Because of the nutrient potassium being mobile, deficiencies are not found very often. Still, potassium deficiencies can be seen in the crop. It can be recognized by the following symptoms:

• Slow or stop in overall plant growth
• Plant hanging loosely under dry circumstances
• Yellow discoloration or dying of the edges of the leafs
• Slow or incomplete flowering

Sometimes a potassium deficiency is called ‘Edge disease’ and should not be confused with a shortage of calcium, which also causes the edges of the leaf to turn yellow or brown. 

How can a potassium and calcium deficiency be distinguished? A shortage of calcium can emerge when a plant does not have enough calcium to take in. This shortage can be recognized by blossom end root, causing yellow-brown to black stains on the bottom of the fruits. A potassium deficiency is showed in several ways. Symptoms vary from dark green, shiny leafs to discoloring bronze leafs and leafs dying early. In tomatoes, this deficiency can be recognized if the fruits do not turn red. 

An excess amount of potassium could negatively affect the plant: 

• Damage caused by sodium (because of reduced intake of water)
• Obstruction of other elements (especially sodium, boron and magnesium)

Even though the chance for the development of a deficiency is small, it is important to keep in mind. Have you spotted signs of a potassium deficiency? Act immediately. The best way to prevent or solve this deficiency, is to add a potassium fertilizer to the plant. If necessary, it can be added to the nutritional feeding schedule if the shortage keeps occurring. This same method of working applies when an excess of potassium is spotted, only the concentration of potassium should be lowered.

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