Assessment of Irrigation Needs in Sugar Beet (Beta vulgaris L.) in Temperate Climate of Kujawsko-Pomorskie Region (Poland)

The primary purpose of this work was to assess the need for irrigation in sugar beet cultivated in the temperate climate of the Kujawsko-Pomorskie region of Poland based on meteorological data from the period 1981–2010. The work was also aimed at determining the tendency of changes in the frequency and intensity of droughts during the period of high water needs for sugar beets (spanning July–August) and confirming the hypothesis that agricultural drought may be identified based on the indicator of meteorological drought—Standardized Precipitation Index (SPI). The occurrence of meteorological droughts amounted to 26.7–40.0%, depending on location. No significant trend of increasing dryness was found; however, quite the opposite, an upward tendency was identified, which indicates an improvement of precipitation conditions over time. It was found that sugar beet production in a temperate climate is carried out in the conditions of precipitation deficits, which amount to an average of 32–49 mm and a maximum of 112–173 mm in July–August, but the deficits showed neither significant nor targeted changes with time. A strong, significant relationship between meteorological (SPI) and agricultural (Pdef) drought indicators allows for a determination of sugar beet irrigation needs solely based on information on normalized precipitation values (SPI).