Assessing the Impact of Reference Evapotranspiration Models on Decision Support Systems for Irrigation

Abstract Reference evapotranspiration ( E T 0 ) is a major estimator for crop water requirements predicted by decision support systems for irrigation. However, the impact of different E T 0 s on the predicted amount of water supply and counts of irrigation events has not been evaluated. Simulations of the Geisenheim Irrigation Scheduling (GS) for vegetable crops with two different E T 0 s, P2- E T 0 and FAO56- E T 0 , were evaluated to assess exemplarily the impact of E T 0 s. The sensitivity of both E T 0 s to local climate conditions was characterized through a random forest analysis, and a linear regression model was used to adjust the original GS by adapting K c -values to the exchange E T 0 . For assessing the outcomes of GS irrigation decision, simulations of 173 individual cropping cycles including six vegetable crops over eight years were conducted. After adjusting P2- E T 0 K c -values to FAO56- E T 0 K c -values, there was no impact of the E T 0 -model on the practical irrigation scheduling with GS. Finally, we discuss that any E T 0 -model, if adjusted accordingly, might have little impact on similar irrigation systems and provide a method to exchange E T 0 s. View Full-Tex