A study was carried out on the sorption of the sparingly water-soluble pesticide linuron in various types of soil with different levels of organic matter. The sorption isotherms of the pesticide were obtained in bath-equilibrium experiments and the data were fit to Freundlich and Dual Reactive Domain Models. In general, the sorption was the highest for the soil with greatest content of soil organic matter. The study also points out the global problem of handling the sewage sludge at wastewater treatment plants. We studied the compost made in Torun's Wastewater Treatment Plant during sludge fermentation. To characterise the compost organic matter UV-Vis and 13C CP/MAS NMR spectroscopy were used. Consequences of the compost use in agriculture are also discussed here. Particular attention is given to the changes in the behaviour of pesticides applied to soil in the presence of compost organic substances. The treatment of soils by the compost from sewage sludge may lead to increased retention or removal of hydrophobic compounds like linuron.