Plant Uses of Potassium (K): Potassium is a macro nutrient and used in a variety of ways. Here are some of the major roles that Potassium plays:

  • Drought Resistance: Stomata are the pores on the leaves that regulate how much carbon-dioxide, water, and oxygen are exchanged between the plant and the air. Low K make the stomata sluggish, causing excessive water loss on hot days and increasing drought stress on the plant.
  • Water Absorption: Potassium cause a gradient drawing water into the roots, low K causes reduces the ability of the roots to absorb water. Low K also reduces the transport of nutrients and water to the rest of the plant.
  • Enzyme Activity: Stabilizes the pH within the plant, and controls the rate at which chemical reactions take place. Required for the production of proteins.
  • Photosynthesis: Low K reduces the amount of ATP (energy) produces and slows photosynthesis. This also slows down the transport of sugars created during photosynthesis to other parts of the plant for storage, and reduces the amount of starch that is synthesized.
  • Crop Quality: Potassium improves the quantity, quality, disease resistance and shelf life of vegetables and fruits. Low K will rob the crops first, even before visible symptoms occur on the rest of the plant.

potassium shortageHow to identify low potassium deficiencies: Significant deficiencies of potassium can be identified as:

  • Yellowing around the leaf edges and tips, and in severe cases the leaf edges may turn brown.
  • Poor flowering
  • Smaller than normal fruit.

Organic sources of Potassium:

Decomposed or Crushed Granite – This is a great conditioner of clay soil and provides a long term (slow release) source of potassium. I’ve found this at Home Improvement stores as it is used for pathways.

Wood Ash – Hardwoods will contain higher percentages of Potassium, however light woods will work too. Wood ash is basic and will raise the pH of your soil.

Sul-Po-Mag – Contains sulfur, potassium and magnesium, and comes from a naturally occurring mineral.

Sulfate of Potash – Also known as Potassium Sulfate.

Muriate of Potash – Also known as Potassium Chloride, the chloride in it is not necessarily what you want to be feeding your soil with, but it does contain potassium and is the cheapest of the potash fertilizers.