A field experiment was established at the Experimental and Didactic Station in Swadzim near Poznań over 2004-2007 (52^o26’ N; 16^o45’ E). The experiment was carried out in a ‘split-plot’ design with 3 research factors in 4 field replications. 2 types of maize hybrids, 6 doses of nitrogen and magnesium doses (including methods of their applications) were examined. The effect of these research factors on the proportion of nutrients and raw material energy value of two types of maize hybrids grown for ear silage were assessed. The hybrid of stay-green type contained less crude fibre but more crude fat in dry matter of ears as compared with the traditional hybrid. The largest amounts of net energy concentration, net energy yield, digestible protein yield and total protein yield were obtained by applying a nitrogen dose of 120 kg N·ha^-1. Fertilizing maize with N + Mg (in rows and by broadcasting), an increase in total protein yield was obtained in relation to the treatments with N fertilization only.

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