•Solute transport in a karst vadose zone studied by 3 long-term tracer tests.•Tracer breakthrough curves monitored over 11 successive hydrological years.•Defined various processes with significant effects on solute transport in karst.•Demonstrated long-lasting storage in the vadose zone of karst aquifers. The processes influencing the solute transport in the karst vadose zone were studied by long-term tracer tests with artificial tracers. The results of three successive tracer tests with different modes of injection were compared. Tracer breakthrough curves were monitored at three drips of different hydrological types inside one of the cave galleries of the system of Postojnska Jama over several years. Comparison of the results indicates the highly significant influence of preceding hydrological conditions (dry vs wet), injection mode (artificial flushing vs natural infiltration by subsequent rainfall, and on a bare rock vs on an overlying layer) and geologic heterogeneities within the vadose zone on solute transport in the karst vadose zone. Injection with artificial flushing resulted in rapid infiltration and the tracer traversed almost one hundred meters of bedrock in hours. However, the majority of tracer can be stored within less permeable parts of the vadose zone and then gradually flushed out after additional abundant and intensive precipitation in the period of several years. Long-continued sampling in each of the tests proved to be important for reliable characterization of the long-term solute transport dynamics.