A two-year pot experiment (2005 and 2006) was conducted to estimate an effect of dredged bottom sediment from Rożnów Reservoir addition to the light, very acid soil on the plant biomass production. The sediment was applied in the amount from 1 to 20% of the substratum mass. Italian ryegrass (Lolium multiflorum L.) and maize (Zea mays L.) were cultivated as the successive test plants. The lowest amount of plant biomass was obtained on the soil (control) and each sediment addition to the substratum caused an increase of the biomass production, both tops as well as the roots of the plant. Larger sediment additions (7% and more) caused a significant increase of the yield, of both the individual plant species and the total biomass during the two years of the experiment. The bottom sediment added to the light, very acid soil distinctly improved the plant yielding and the way of biomass utilisation should be assessed on the basis of its chemical composition analysis.