The effect of liming on uptake of copper by white mustard (Sinapis alba L.) was evaluated when applied alone or in conjunction with earthworm humus in detoxification of light (sandy) soil polluted with excess copper. The study consisted of two-factor pot trials (first-rate factor – degree of soil contamination: 0, 75, 150, 300, and 450 mg Cu·kg^-1 of soil; second-rate factor – variants of application of CaCO₃ and earthworm humus (EH)). In the absence of any remedial treatment, phytotoxicity of copper at a concentration of 75 mg Cu·kg^-1 decreased the mustard yield by 60%, while at 150 mg Cu·kg^-1 the loss of yield was over 90% compared to natural soil. Both CaCO₃ and EH reduced Cu uptake. High effectiveness of liming with a CaCO₃ dose according to double hydrolytic acidity (2 Hh) in detoxification of the analyzed soil was demonstrated. Simultaneous introduction of EH in the amount of 1.5% of soil weight resulted in Cu uptake reduction and the same metal concentration decrease in plant foliage tissues. The highest value of plant tolerance index (yield on polluted soil/yield on control soil), was obtained under joint application of CaCO₃ according to 2 Hh+EH 1.5%. Indices of Cu bioaccumulation (increase of Cu concentration in plant/increase of Cu concentration in soil), tend to decrease as soil contamination increases, implicating a depressed ability of white mustard plants to accumulate this element in its aerial parts.