What is the primary source of potassium (K)?

The primary source of potassium (K) in soils is potassium-bearing minerals. These minerals are naturally occurring materials found in the Earth's crust. When these minerals weather and break down over time, they release potassium ions into the soil, making them available for plant uptake. This process is essential since potassium is a vital nutrient required for various plant functions, including photosynthesis, enzyme activation, and the regulation of stomatal opening.

While organic matter can contribute potassium to the soil as it decomposes, it typically does not serve as a primary source compared to mineral sources. Rock phosphates are more associated with phosphorus rather than potassium, and peat moss, while beneficial for soil structure and moisture retention, is not a significant source of potassium. Therefore, potassium-bearing minerals are recognized as the main source due to their abundance and the efficiency at which they contribute to potassium availability.