The Role of Potassium (K) in Fertilizers - Mivena

Potassium (K) is traditionally known as one of the three essential macronutrients in fertilizer, together with Nitrogen and Phosphorus (NPK). Today Calcium and Magnesium are also recognised as key elements, yet Potassium remains one of the most influential nutrients for plant performance. Although it does not build plant tissues, it regulates a wide range of physiological processes that determine growth, quality and resilience.

Where Potassium Comes From?

Potassium is a chemical element with the symbol K and is closely related to Sodium (Na). In its pure form it reacts immediately with oxygen. Historically, it was obtained from the ashes of burnt plant material. This origin explains the English name Potassium and the Latin word Kalium.

Modern Potassium production relies on large underground salt deposits that were once ancient lakes or seas. The largest deposits are in Canada. Additional sources include evaporation-based extraction from the Dead Sea. After mining, the salts are separated and most Potassium ends up as Potassium Chloride (KCl), known as muriate of potash or MOP.

What is the role of K in fertilizers?

Around 95 percent of all Potassium produced worldwide is used for plant nutrition. In plants the concentration of K usually varies between 0.5 and 2 percent of the dry weight. Potassium is not a building block like nitrogen or calcium. Instead it acts as a regulator of many key functions inside the plant.

In general the plants Potassium makes plants “harder” by maintaining turgor pressure of cells, which keeps them from wilting.

Furthermore, Potassium plays an important role in proper functioning of stomata which control the “breathing” of plants. It regulates the opening and closing of stomata. These microscopic pores allow plants to absorb carbon dioxide and release water vapour. When K levels are adequate, stomata respond quickly to environmental changes. This results in:

• Efficient photosynthesis
• Improved water use
• Better resilience under drought and heat

How Potassium Moves Energy Through the Plant

Potassium is essential for moving water, nutrients and sugars inside the plant. This movement supports strong roots, healthy leaves and good distribution of sugars toward flowers and fruits. Fruit size, flavour, colour and shelf life all rely on proper potassium supply.

How Potassium Helps Build Plant Energy

Potassium activates many of the enzymes that help form proteins, starch and energy compounds. When potassium is low the plant can still produce sugars, but it struggles to use them effectively. Growth becomes less efficient and the plant becomes more sensitive to stress.

In practice, K-rich fertilizer is used by growers to make the plants harder and more resistant to stress such as cold and drought. Potassium is used by crop producers to enhance fruit-size, -quality and -flavor. In turf, K is used to make turf harder and more drought resistant.

Recognising Potassium Deficiency

Potassium is mobile inside the plant which means deficiency symptoms first appear on older leaves. Typical signs include:

• Yellowing or browning of leaf edges
• Necrosis at advanced stages
• Reduced vigour and slower growth
• Increased sensitivity to drought, cold and disease

In turf these symptoms appear as yellow leaf tips, reduced density and weaker recovery after wear or damage.

How does Mivena apply K?

Mivena works in many segments ranging from high-end golf courses in Southern Europe to soft-fruit growers in Eastern Europe and public sports fields in Scandinavia. Each sector has different application strategies, yet several principles apply universally.

Balance of N and K Throughout the Growth Cycle

At the beginning of growth plants usually require more nitrogen. During the mid growth phase the balance moves toward N and K in equal proportion. Toward the end of the cycle the demand for potassium increases. The exact timing depends on the crop and the environmental conditions.

Balance of N and K Throughout the Growth Cycle

Potassium Use in Turfgrass Management

In turfgrass the need for Potassium rises in early summer when the grass must withstand heat, drought and wear. During autumn and winter turf also benefits from higher K levels to endure cold conditions. Recommended N to K ratios in turf commonly range between 1:1 and 1:2.

Why Mivena Does Not Recommend Potassium Nitrate in Autumn and Winter

Some customers request Potassium Nitrate (KNO₃) for late season applications. This is not ideal because:

• The longevity of KNO₃ is very short
• Nitrate-based nitrogen produces soft and disease-prone growth in cold seasons
• There is a higher risk of nutrient leaching
• Turf becomes more sensitive to fungal pressure

Potassium Sulphate is preferred in colder months due to its slower release pattern, lower salt impact and more stable interaction with Ca and Mg.

Coated Potassium Nitrate can be useful in nurseries for release periods longer than four months. For turf it is generally not cost efficient. Standard Potassium Sulphate provides a similar release window of approximately three to four months.

Potassium in Nurseries and Soft-Fruit Production

Ornamental Nurseries

Potassium influences compactness, strength and plant habit. Growers often use Horticote Plus during substrate mixing and Horticote Topdress for additional nutrient supply during the crop cycle.

Soft-Fruit and Fruit Growers

Potassium plays a major role in fruiting crops. It affects flowering, fruit set, size, colour, sugar levels and firmness. Growers often increase K to achieve N to K ratios of 1:3 or 1:4, especially through fertigation using Granusol or Granufert high K formulas.

Mivena products with high K:

- Granucote CRF 12-5-24
  Especially suited for fairways. Will be applied in September/October with durations to last until February/March of the next year.

- Greenstar CRF 15-0-22
  A slightly coarser granule than Granucote and only available in 3M durations. Is often used in Fairways and Roughs, but also in landscaping and garden maintenance.

- Granuform SRF 16-0-22 / 19-0-19 / 19-5-17
  Very small granule, extremely suitable for Tees and Greens. Will give enough nutrients for 2-3 months.

- Granusports SRF 8-0-26 / 19-5-17 / 19-0-19
  Similar to Granuform except a larger granule. Is more suited for sports fields and some tees. Will also give enough nutrients to turf for 2-3 months.

- Horticote Plus CRF 14-10-18 + Traces
  Available in 4-6-8-12 Month durations. 100% coated NPK granules, very suitable for mixing in substrates for longer grow-periods.

- Horticote Topdress 14-7-20 + Traces
  Partly coated fertilizers used to apply on pots where the plant is already established. Suitable for nurseries that need to give a little extra dose of fertilizers to generally larger pot-sizes

- Granusol WSF 10-10-30 / 12-7-25 / 4,5-11-36
  Highly soluble crystalline powder that is suitable for any form of irrigation. All formulas contain a high dose of trace-elements and Mivena’s special vitamin mixture with many benefits that improve plant vitality, health and nutrient uptake

- Granufert WSF 6-8-30 / 10-5-23 / 13-6-24
  Highly soluble powder that is most suitable for fertigation systems. Some products contain additional CaO for improved fruits

Conclusion

Potassium is far more than an add-on nutrient. It is a central regulator of plant physiology and directly influences:

• Photosynthesis efficiency
• Water management and stress tolerance
• Fruit size, quality and flavour
• Compactness and strength in ornamentals
• Turf resilience, density and recovery

For growers, greenkeepers and agronomists, Potassium is one of the most strategic levers in any fertilization plan. Choosing the right K source at the right time and in the correct balance with other elements is essential for achieving high performance in any crop or turf situation.

Stefan Hoefnagel – Technical commercial responsible at Mivena