The most common high potassium fertilizer is murate of potassium, but potassium sulfate provides almost as much of the mineral without damaging soil. In soil, potassium exists as the ion, fixed in minerals that release it slowly, and an unavailable mineral form. Most of the naturally occurring phosphorous in the soil is in the unavailable mineral form.
Potassium helps to increase crop yield by improving drought resistance in plants. It encourages healthy root development and aids in photosynthesis. It aids in storing sugars and increases the protein the plant provides. In fine soils, such as clays, the fertilizer requires tilling to reach the root zone, although it leaches to them through sandy soils.
In areas where potassium levels are generally high in surrounding areas, have the level of potassium in the lawn or garden tested before applying more. In specialty applications, as with pot plants and hanging baskets, specialty fertilizes, such as water soluble ones may provide the best option. In lawns, slow release fertilizers provide small amounts of the mineral over time to ensure the grass has the best chance to absorb and use it.
Peanuts, cotton, grain sorghum and corn require large amounts of potassium. However, fescue and alfalfa remove the most potassium from the soil at the time of harvest.