The Breakdown of Soil K and Why it Matters for Plant Growth
Potassium: An Important Nutrient for Plant Growth

Potassium (K) is essential for plant growth and it has long been recognized that potassium fertilizers are beneficial. Plants need potassium to grow, maintain tissues and reproduce and so they fight with other nutrients for their attention. It is important for plants to have a balance of nutrients in order for them to grow and produce healthy fruits and vegetables. Potassium is one of the key nutrients that a plant needs. It helps the plant form proteins, which are necessary for photosynthesis, and it also helps with water absorption. 

What is Soil K?

Soil K is a form of plant nutrient that is used to correct the soil’s potassium level. This form of potassium is different from the one found in fertilizers, which are usually nitrogen-based. The solution to nitrogen deficiency in soil is not just more nitrogen, but more potassium. The lack of potassium will cause plants to be stunted. Soil K is a natural form of potassium that can be added to the soil without the need for nitrogen fertilizers. This solution helps create a healthy and viable crop or garden without the negative effects that come with too much nitrogen. 

Why is Soil K Important?

Potassium is an important nutrient for plant growth. It is a major cation in the plant cell and helps to maintain the osmotic balance of the cell. Potassium also plays a role in water uptake and distribution, nitrogen fixation, photosynthesis, protein synthesis, and enzyme activation. In plants, potassium ions are found mainly in the vacuole and play an important role in maintaining water balance by regulating turgor pressure. The high concentration of potassium ions outside the vacuole creates an electrochemical gradient that drives potassium into the vacuole through active transport. This gradient is maintained by two types of ATPases: H+-ATPase which pumps protons out of the vacuole to create a proton concentration gradient across its membrane; and K+-ATPase which pumps potassium ions into the vacuole to create a high concentration outside it. 

What Happens if Plants Don't Get Enough Soil K?

Plants need potassium to grow and maintain their cellular structures. Potassium deficiency symptoms include smaller leaves, yellowing of the leaves, brown patches on the leaves, and stunted growth. There are many causes for potassium deficiency in plants. The most common cause is a lack of potassium in the soil. This can be caused by over-fertilizing or by not fertilizing at all. Another cause of potassium deficiency is when there is too much salt in the soil, which can leech out potassium from the soil and prevent it from being absorbed by plants.

Other symptoms of potassium deficiency in plants include:

  1. leaf scorching
  2. leaf curling
  3. brown spots on leaves
  4. stunted growth
  5. poor fruit production
  6. slow plant growth

Potassium deficiency in plants can be caused by the following:

  1. Too much nitrogen in the soil
  2. Lack of potassium in the soil and/or lack of sunlight
  3. Too much water or too little water
  4. Plant diseases such as powdery mildew

How to Increase Soil K Levels to Support Plant Growth

A soil’s pH level is a measure of the soil’s acidity or alkalinity. The scale ranges from 0-14, with 7 being neutral. A pH level below 7 indicates acidic soil and a pH level above 7 indicates alkaline one. The optimal soil pH for plants is between 6.5 and 7.5, so if your plants are not growing well it may be because their roots are not absorbing nutrients properly due to low levels of potassium. We can increase the K level in soil by adding compost or other organic materials. Composting is one of the most important ways to increase soil K levels because it adds nutrients to the soil and helps it retain moisture. Composting also creates a healthy environment for microbes, which helps break down dead plants and animals so they can be used by plants as nutrients.

Further Reading

Kilmer, V. J., Younts, S. E., & Brady, N. C. (1972). The role of potassium in agriculture. American Society of Agronomy.

Römheld, V., & Kirkby, E. A. (2010). Research on potassium in agriculture: Needs and prospects. Plant and Soil, 335(1-2), 155–180. https://doi.org/10.1007/s11104-010-0520-1

Sardans, J., & Peñuelas, J. (2021). Potassium control of plant functions: Ecological and agricultural implications. Plants, 10(2), 419. https://doi.org/10.3390/plants10020419

Zörb, C., Senbayram, M., & Peiter, E. (2014). Potassium in agriculture – status and Perspectives. Journal of Plant Physiology, 171(9), 656–669. https://doi.org/10.1016/j.jplph.2013.08.008

Öborn, I., Andrist-Rangel, Y., Askekaard, M., Grant, C. A., Watson, C. A., & Edwards, A. C. (2008). Critical aspects of potassium management in Agricultural Systems. Soil Use and Management, 21(1), 102–112. https://doi.org/10.1111/j.1475-2743.2005.tb00114.x