Summary:

Irrigation requirements of forest nurseries localized on a sandy soil in the years 2000-2009 in vicinities of Bydgoszcz, Chojnice and Toruń, are compared in the paper. It was found that the water use of the soil layer with controlled moisture calculated for the whole vegetation period (April-September) was the highest in the vicinity of Toruń (524 mm), the lower - in the vicinity of Bydgoszcz (504 mm), and the lowest - in the vicinity of Chojnice (498 mm). The highest monthly water use for evapotranspiration was found in July. This index was the highest for Toruń (126 mm), the lower - for Bydgoszcz (121 mm), and the lowest for Chojnice (116 mm). Seasonal irrigation needs of a forest nursery was the lowest in vicinity of Chojnice (116 mm), the higher in the vicinity of Toruń (170 mm), and the highest in the vicinity of Bydgoszcz (183 mm). The highest monthly irrigation needs - on average for ten years studied - were occurred in June and the lowest - in September. But, these needs were characterized by the very big variability in particular years. In case of uniform rainfall distribution in a particular month, no needs of irrigation would be occurred in investigated ten-year period during 18 months (from among 60 taken into consideration) in the vicinity of Chojnice, as well as during 13 and 10 months in vicinities of Bydgoszcz and Toruń, respectively.