Irrigation requirements and irrigation water use efficiency in Slovakia in the period 1961–2020

Numerical simulations by the DAISY model were performed for the period 1961–2020 with series of daily data on global radiation, air temperature, air humidity, wind speed, and atmospheric precipitation from meteorological stations representing each region in Slovakia. The simulations were run aiming to evaluate the irrigation need and irrigation water use efficiency of field crops: spring barley, winter wheat, maize, sugar beet, and potato. Also, dominant soil types were taken into consideration like Chernozem, Luvisol, Fluvisol, Mollic Fluvisol, and Phaeozem. The irrigation water use efficiency values obtained from numerical simulations are like the values obtained from the field stationary experiment. The most significant increase in the need of irrigation in the period 1991–2020 was evident in the southwest of the Danube Lowland on the upper Žitný ostrov (Rye Island). The highest increase in the moisture requirement of crops in the period 1991–2020 compared to the period 1961–1990 was recorded in the west and north of the Danube Lowland. There was a decrease in the irrigation water use efficiency for crops grown in the summer season. In the case of dense cereals, there was a reduction in the irrigation water use efficiency of mainly in the south of central Slovakia, in the Zvolenská basin, in the regions of Turiec, Šariš and Spiš. The highest average irrigation need was calculated for the area of the Danube and Záhorská Lowlands.