Field experiments were carried out at the Didactic and Experimental Farm in Swadzim near Poznań in the years 2004-2007. The experiment was carried out in a „split-plot” design with 3 experimental factors and 4 field replications. Two cultivars were studied (Anjou 258 and LG 2244 – stay-green type), 6 doses of nitrogen (0 kg N ha-1, 30 kg N h-1, 60 kg N ha-1, 90 kg N h-1, 120 kg N h-1, 150 kg N ha-1), and one dose of magnesium and method of Mg fertilizer application (0 kg MgO ha-1, 25 kg MgO ha-1 – in rows and 25 kg MgO ha-1 – broadcasting). The effect of experimental factors on the yield of maize plant dry matter and its content in the phase of 5-6 leaves and during harvest were analysed. A better dynamics of dry matter accumulation in the initial developmental phase was shown by the hybrid LG 2244 (stay-green type) as compared with Anjou 258 cultivar. During harvest, this relation was inverted. The dose of nitrogen modified the yields of maize dry matter in the whole period of maize growth. The applied magnesium fertilization increased the yield of dry matter of straw, cobs and of whole plants. The application of magnesium by broadcasting proved to be a more effective method, as compared with row application.