Soil samples taken after the completion of the second round of the crop rotation (potato – spring wheat – pea – winter wheat) were used to determine the species composition, and the number and distribution of weed seeds. Reduction in the number of ploughings to three in the crop rotation decreased the pool of weed seeds in the 0-30 cm of soil layer, whereas when only one ploughing was made the number of weed seeds was greater than after conventional tillage. Higher level of fertilisation significantly (by about 30%) increased the weed seed pool in the soil. Among the small number of weed species determined, the dominant species were mainly Chenopodium album, and – to a lower extent – Galinsoga sp. and Viola arvensis. Irrespective of tillage method and fertilisation level, the greatest numbers of weed seeds were determined in the 5-15 cm layer of the soil, l1.3% less in the deepest horizon (15- 30 cm), and the least (by 31.5%) – in the surface layer of the soil.