Summary:

The aim of this study was to estimate the water demand for sugar beet in Chełmno County, depending on projected climate change. The study considered two scenarios (RCP 4.5 and RCP 8.5) for the period 2021-2100. Based on the calculations, it was concluded that sugar beet plants will require the most water in July for proper growth and development. Daily water demand in this month - in average, moderately dry and very dry years, respectively - will be amounted 4.3 mm, 4.7 mm and 5.2 mm under the RCP4.5 scenario, while in the RCP8.5 scenario they will be higher - at 4.4 mm, 4.9 mm and 5.3 mm, respectively. Sugar beet water needs throughout the growing season (April 21 - September 30), if climate change unfolds according to the RCP4.5 scenario - in average, dry, and very dry years - will be amounted 475 mm, 523 mm, and 570 mm, respectively. However, under the RCP8.5 scenario, they will be higher, reaching 492 mm, 541 mm, and 590 mm, respectively. The linear regression equations determined for the forecast period (2021-2100) indicate that the water needs of sugar beet are expected to increase. For the RCP4.5 and RCP8.5 scenarios, the water needs of sugar beet during the growing season (April 21-September 30) will increase by 4.1 mm and 10.3 mm in each decade. Rainfall deficiencies throughout the sugar beet growing season - according to the RCP4.5 climate change scenario - in average, dry and very dry years - will amount to 141 mm, 246 mm and 327 mm, respectively, while in the RCP8.5 scenario they will be greater, reaching 145 mm, 251 mm and 336 mm, respectively. The calculations show that - on average for the eighty-year period 2021-2100 - higher increases in sugar beet root yield (37.3 t/ha) will be possible to achieve due to irrigation if climate change proceeds according to the RCP4.5 scenario than in the RCP8.5 scenario (35.3 t/ha).