Studies were carried out on samples obtained from a field experiment conducted on light loamy soil in 2002-2004. The experiment was set up as randomized sub-blocks with three replications. Two methods of soil tillage, conventional and simplified, were compared as well as seven weed control methods including application of herbicides or their mixtures: Plateen 41,5 WG, Plateen 41,5 WG + Fusilade Forte 150 EC, Plateen 41,5 WG + Fusilade Forte 150 EC + adjuvant Atpolan 80 EC, Barox 460 SL, Barox 460 SL + Fusilade Forte 150 EC, Barox 460 SL + Fusilade Forte 150 EC + adjuvant Atpolan 80 EC and control object (mechanical weeding). Magnesium content and its removal by potato tuber crop significantly depended on soil tillage methods, weed control methods and weather conditions over the growing season. More magnesium was contained in tubers harvested from the plots where reduced tillage had been applied (1.771 g kg-1 on average), compared with 1.762 g kg-1 under the conventional method. Herbicides and their mixtures applied to control weeds in the potato field significantly increased magnesium content in tubers and its removal by tuber yield by an average 2.7% and 11.0%, respectively, compared with the control where weeds were controlled by means of mechanical cultivation.