Field trials have been carried out in a five-year period (2002-2006) at the Experimental Station in Swadzim (52º26’ N; 16º45’ E), of the University of Life Sciences in Poznań. Six maize hybrids from different maturity groups: FAO 200 (Oleńka and PR39T68), FAO 240–250 (Blask and Matilda), FAO 260–270 (Clarica and Anjou 258) have been tested to find relations between the length of developing periods, as well as the accumulated temperature and total precipitation, and the grain yield of selected maize genotypes. During the trial period, lower precipitation was observed compared with the mean value for the region, and a particularly high deficiency was noted in 2006. The hybrids yielded according to maturity groups, i.e. grain yields increased with elongation of the vegetation period. Weather conditions caused higher variability of grain yield compared with single yield components. The highest influence on maize yield was caused by weather conditions during the period from tasseling to full maturity. Grain yield of all hybrids was more strongly modified by total precipitation than by accumulated temperature during this period.

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