Water Productivity and Irrigation Water Demand of Potatoes in Brandenburg (Germany) Between 1902 and 2020

The aim of this publication was the derivation of reference values of the water productivity of fresh matter of potatoes (WP_FM) with and without irrigation for Brandenburg (Germany). Furthermore, reference values of the irrigation water demand (IWD) were derived. For this purpose, the AgroHyd Farmmodel was used. Calculations were performed within two time periods, 1901–2010 and 2000–2020. The relationships between the traits were detected. The calculations were made for each county of Brandenburg. The water productivity of irrigated potatoes (WPirri) varied between 6.66 and 9.19 kg FM m⁻³. The irrigation water demand (IWD) of potatoes in each county varied between 173 and 212 mm. In the last 20 years, the trend of the irrigation water demand became positive. Irrigation water seems to be not always able to satisfy the water demand of the potatoes—the yield and, closely associated with the yield, the WPirri decreased. Water productivity of rainfed potatoes (WPnoirri) decreased with increasing precipitation (P). High yields and low water inputs leading to a higher WPnon-irri seem to be not realistic. The high yields during high IWD seemed to be only possible with irrigation. The focus for improving the water productivity has to be put on the large differences in water productivity between the counties. In counties with lower P and lower available water capacity, the increase of irrigation water use to increase WP should be planned carefully.