Q.why would potassium be high in soil test when no amendments have ever been added to area?
as above
As with all beneficial soil components, too much potassium can be detrimental to plant growth, as it interferes with the uptake of other substances.
If a soil test indicates a high level of potassium, literally start from the ground up by not adding more to it in the form of a multipurpose fertilizer. Typical fertilizer blends are generally composed of the three most important substances -- nitrogen, phosphorus and potassium -- which are indicated on the packaging by the letters N, P and K. Selecting a blend that is low in potassium, or K, or contains none at all, is a first step in assuring that it doesn't build up to unsuitable levels in the soil.
If a soil test indicates a high level of potassium, literally start from the ground up by not adding more to it in the form of a multipurpose fertilizer.
Schedule any fertilizing within several weeks before planting, so that the potassium doesn't have time to accumulate during the off-season. To minimize long-term potassium buildup, consider using aged or composted animal manure as a substitute for commercial fertilizers, as its components break down more slowly to keep up with plant demand. If using manure, apply it at a rate of 40 pounds for every 100 feet, and work it into the soil to a depth of 6 to 9 inches.
https://extension.umd.edu/sites/extension.umd.edu/files/_images/programs/hgic/Publications/HG42_Soil_Amendments_and_Fertilizers.pdf
