The trials were carried out in 2005 and 2007 at the Experimental Station Swadzim (52^o29’ N; 16^o46’ E) of the University of Life Sciences in Poznań. The goal of two-factorial trials was to evaluate a decrease in yield of grain and plant raw material for ensiling from F2 maize generation compared with F1. The decrease in grain yield in F2 depended on vegetation conditions and the cultivar. In the unfavorable season for maize growing, the average decrease for cultivar amounted to 3.16 t·ha^-1, i.e. 31.8%, while in the favorable season, this was 2.81 t·ha^-1 and 23.5%, respectively. The losses caused by a decrease in grain yields in F2 significantly exceeded the cost of seed material. In 2005 these amounted on average up to 781.4 PLN·ha^-1, and in 2007 – 1525.3 PLN·ha^-1. The yield of raw material for ensiling was also lower from F2 generation and on average amounted to 6.71 t·ha^-1 (21.2%) in 2005 and 5.68 t·ha^-1 (8.8%) in 2007. Moreover, the raw material for ensiling from F2 had lower cob content compared with F1.

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