Aim of the study:
Indication of changes in maize yield for grain and silage in connection with the observed climate changes.

Material and methods:
Data from field experiments of the experimental station of the University of Warmia and Mazury since 1972 as well as meteorological data (air temperatures and precipitation). Calculations using the trend analysis of original variables and determined indexes (GDD, SPI, Sielianinov indexes), weather-yield linear models and elements of spectral analysis.

Results and conclusions:
Changes in thermal conditions were demonstrated based on average air temperatures and the GDD index. There were no significant changes in atmospheric precipitation, showing a small periodicity of ten years, and no changes in the frequency of months with a deficit of precipitation (SPI analysis).  It was proofed that changes in thermal conditions as well as the introduction of new maize varieties over fifty years significantly improved plant maturation which resulted in a significant increase in grain weight. However, it did not affect the yield of maize for silage, neither in crop rotation nor in the monoculture system.