Problem Identifier / Potassium Deficiency in Plants

How to Fix A Potassium Deficiency In Plants

Potassium Deficiency Cannabis Plant
Potassium deficiency in a cannabis plant.

Potassium is one of the essential nutrients for plants. Large quantities are required for reproduction and correct growth. The only nutrient more essential for plants than potassium is nitrogen. For this reason, potassium is often called the quality nutrient. Potassium affects the size, color and shape of the plant in addition to the taste of the fruit.

Potassium is important for photosynthesis by regulating CO2 uptake and the stomata‘s opening and closing. Enzymes essential for producing ATP are activated by potassium. Plants require ATP for numerous chemical processes required for the correction of plant issues. Potassium is critical for regulating water within the plant, the absorption of water through the roots and the loss of water due to the stomata.

Potassium provides plants with better drought resistance. Potassium is necessary throughout starch and protein synthesis. Potassium activates the enzyme necessary for starch synthesis. Potassium also activates a lot of the enzymes that plants require for healthy growth.

How Does a Potassium Deficiency Affect the Quality of Your Plant?

The plant quality is affected by some or all the following:

  • Often impacts the older leaves near the top
  • Leaves turn brown or yellow
  • Burnt edges and tips
  • Margins of the leaves turn yellow

In most instances, a potassium deficiency in plants first appears on the older leaves. The quality of the upper leaves is also negatively impacted resulting in brown or yellow leaves with burnt tips and edges. The burnt edges resemble a nutrient burn, but the difference is the margins of the leaves begin to turn yellow. Either the yellowing or burnt edges can appear first. If both symptoms appear, it is almost certain there is a potassium deficiency in plants.

Potassium Deficiency Symptoms in Plants

Potassium Deficiency Soybean Plant
Potassium deficiency in a soybean plant.

The symptoms of a potassium deficiency in plants include:

  • Curling leaves
  • Leaf edges burn, turn brown and die
  • Leaves turn brown, yellow or white
  • Inner veins remain green
  • Leaf edges turn light green

The symptoms include curling tips, brown edges, leaf burns and death. The leaves turn brown, yellow or white with a burnt appearance. The inner veins usually remain green. Overwatering the plants can make the deficiency much worse because potassium moves freely within the plant from the roots to the upper branches and leaves. If there is not enough potassium in the soil for the whole plant, the initial symptoms first appear on the leaves.

The common symptom is yellowing tissue appearing around the edges of some of the leaves. Entire leaves can turn a light green if the deficiency progresses. Cannabis plants grown under HPS or LED grow lights often have the appearance of a burn.

Possible Confusion with Other Symptoms

  • Light burn is frequently mistaken for a potassium deficiency due to similar symptoms
  • Burnt edges and tips resemble nutrient burn
  • Root issues can resemble a potassium deficiency
  • Diseases
  • Yellowing between the veins occurs with a magnesium or manganese deficiency

What Causes a Potassium Deficiency?

The most frequent causes include:

  • Sandy soils
  • High levels of magnesium, calcium or salt in the soil
  • High pH range
  • Extreme over liming
  • Low soil oxygen
  • Stressful conditions
Potassium Deficiency Potato Plant
Potassium deficiency in a potato plant.

A potassium deficiency is common if the plant is grown in sandy soils due to leaching. Water moves through sandy soil quickly, resulting in important nutrients including potassium being carried away from the roots of the plant. High levels of magnesium, calcium or salt in the soil can result in a potassium deficiency even if there is plenty of potassium contained in the soil because the nutrient is unable to be absorbed.

If the pH range of the soil is high, the result is frequently a potassium deficiency in plants. Over liming affects the soil, leading to a deficiency in numerous nutrients. Extreme moisture or compaction decreases the level of oxygen in the soil causing a potassium deficiency. Other causes include transplanting, heat and overwatering.

How to Fix a Potassium Deficiency in Plants

A deficiency can be treated by using the following options:

  • Move grow lights farther away from the plants
  • Use high-quality soil
  • Make necessary adjustments to the pH range
  • Closely watch the leaves of the plant to ensure recovery

If a plant is too close to growing lights, the result is often a light burn with a close resemblance to a potassium deficiency. Plants should be kept a minimum of 12 inches away from powerful HPS and LED lights. Moving the plants a few inches more can prevent the issue from advancing. Using high-quality soil is important to ensure the plants receive enough potassium for optimal health.

Potassium Deficiency Marijuana Plant
Potassium deficiency in a cannabis plant.

Plants absorb potassium better when the pH range is lower. Higher levels can result in the symptoms of a potassium deficiency despite there being enough available close to the roots. A potassium deficiency can occur because the pH range is too high for adequate absorption. The roots of plants grown in soil need a pH level of 6.0 to 7.0. When the growing medium is either coco coir or hydro, the best range is 5.5 to 6.5.

If a potassium deficiency is suspected, the system needs to be thoroughly flushed. Clean pH water is the best option provided the correct nutrients including potassium are available. Only growth showing newer signs of damage is likely to recover. Plants should be watched for several days to be certain the new growth is not showing any symptoms of a potassium deficiency.

How Long Does It Take for a Plant to Recover from a Potassium Deficiency?

Do not expect recovery from any older damage. Watch the new growth carefully for several days to make certain there are no signs of a potassium deficiency. The issue should be completely resolved within four to seven days.

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