The authors present a method for soil sample compaction and propose especial equipment for this purpose. In this paper some results are given of compaction of two soils, by the water content and the intensity of compaction. Compacted soil samples were obtained in order to get an increasing scale of bulk densities. On these samples rice was planted to determine the ratios between rot penetration of the test plants and bulk desities of the soil. The authors were able to find out that from determined values of bulk densities artificially obtained, the rice roots were unable to penetrate the compacted soil samples and the development of the root system was largely reduced.