In the pot experiments conducted on the four mountain meadow soils with high reserves of soil potassium, a possible supply of this clement for rye grass supply was examined, when potassium was excluded or its dose was limited in the fertiliser. Differences in potassium removal with yield during exhaustive cultivation were difficult to justify using both static and dynamic indicators of plant supply with potassium. Thus, dynamics of potassium trans formations in the soil corresponding to the uptake amount, was assessed through the speed with which reserve potassium was passing into the solution using oxalic acid, and by the share of potassium from unexchangeable forms in the removal of this element removal with ryegrass yield.