Deficiency and excess of Potassium in cannabis plants

Potassium

There are many nutrients that influence in the development of marijuana plants; on this post, we are going to point out the most important functions of Potassium. We will tell you how to treat deficiencies and excesses of this element and the effect it has on the plant metabolism, especially in cannabis plants.

Potassium is an element found in the land in mineral form. This mineral is more or less present according to the type of terrain. Soils composed of clay are by far the richest ones in potassium, containing up to a 3%.

The potassium cycle

This element arrives at the oceans and seas through rain, aquifers, rivers, etc, where it returns by evaporation to the sky in the form of water vapour. This vapour condensates and returns to Mother Earth in form of rainfall..

One of the ways that potassium has for its self-regeneration in the land is through animal droppings. Potassium returns to dry land to be processed again by micro-life. The remains not used by plants will be swept away by the rain and led through aquifers into the seas and oceans to return again to solid ground and close the potassium cycle.

In those regions with constant rainfalls, the substrate doesn’t properly retain this nutrient, so it isn’t found  in the substrate in sufficient quantity for plants. Potassium is easily carried away by water, so we should add potassium in the form of sulphates to out nutrient solution in order to make it available for plants.

Functions of potassium in cannabis plants

Potassium is one of the most important nutrients for marijuana plants, and although it doesn’t have much presence in the plant tissues it performs important catalyzer functions in many metabolic processes as those we list below:

• It takes part in the photosynthesis process improving the synthesis carbohydrates.
• It participates in the synthesis of proteins and amino acids, which come from nitrogen in the form of ammonium, so the interaction between these two nutrients is vital to perform different metabolic processes of plants.
• It improves the resistance of plants during drought periods.
• It increases the consistency and strength of the plant tissues.
• Together with Phosphorus, it improves  the strength and resistance of the root system.
• The resistance against frost is also increased by acting in the sap of the plant.
• It increases the weight, density and volume of the buds.

If there is a potassium deficiency, plants will have visible symptoms that will help us to detect it. Potassium is a mobile element so it moves from older to younger leaves when needed, since the top part of the plant has always more metabolic activity. We should make sure that our plants have enough Potassium during their life, since any lack of this nutrient will be translated into lower yields.

In the case of having potassium deficiencies, you should add more fertiliser (rich in this element) either from organic or mineral origin. Organic fertilisers are more slowly processed than mineral nutrients, which will correct this deficiency in no time and will allow you to harvest decent buds. If the deficiency is at an early stage you can simply increase the dose of your organic or mineral nutrient, what will probably solve the problem.

Potassium deficiency in cannabis plants

Visible symptoms in cannabis plants:

• The leaves turn yellow from the tips towards the centre, ending at the base of the leaf.
• Plants are weak and have little resistance to diseases.
• Stems are also weak and bend easily.
• The final yield of buds is seriously reduced.
• An excess of calcium can lessen the capacity of the plant to absorb potassium, leading it to a deficiency of this element.

Potassium excess

Symptoms of potassium excess:

• Blocks the absorption of other elements such as calcium, magnesium, zinc and iron.
• Given this situation, you should flush the roots with at least triple the amount of water than the capacity of the pot; you can also add any component that helps to flush the salts away and leach the substrate. Then, you should water with a light, complete and balanced nutrient solution.

The plant in the picture #1 presented a potassium  deficiency that has been treated on time, without losing much bud yield and quality.

This marijuana plant was grown in an inert medium - coco-coir - and suffered a deficiency during the flowering stage, when potassium is more needed, during the 6th and 7th weeks (This plant had a flowering period of 8-9 weeks)

In the picture #2 we can see how the plant has suffered a more serious potassium deficiency.

At medium height of the plant we can see how the tips of the larger leaves are burned. Moreover, you can see with ease a discoloration of the leaves to a more yellow colour.

At the top of the plant we can easily detect that the plant has been negatively affected by this deficiency. The buds couldn’t develop completely and have remained in a quite decayed condition..

The buds of this plant won’t have superior smell or flavor since potassium is essential in terpene production.

At this stage, if you didn’t provide the necessary nutrients the yield will be seriously decreased. The buds won’t be compact and the resin production will be minimal.

These deficiencies are usually more evident and frequent in Indica strains, which are often grown without much knowledge since their flowering stage is much faster than Sativas, and the maximum demand for potassium is centralized in no more than 1-2 weeks, depending on the strain.

Since Sativa plants take much longer to flower, their nutritional needs are more progressive than in the case of Indica genetics. Still, it should be noted that Sativa strains are more susceptible to be over-fertilised than Indicas, so you should pay close attention to their needs to have a crop free of deficiencies and excesses.

In this way, choosing a balanced hybrid strain will help  to control any excess or deficiency of potassium and other minerals like nitrogen or phosphorus.