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 0s 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 0s, P2-E T 0 and FAO56-E T 0, were evaluated to assess exemplarily the impact of E T 0s. The sensitivity of both E T 0s 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 0s.
Highlights
Water resources are limited; the worldwide water demand is increasing with a growing population and industry [1]
Irrigation scheduling based on estimating crop water requirements with reference evapotranspiration (ET0 ) and crop coefficients (Kc -values), called “crop water balance (CWB)”, is internationally well-established [4,5]
This study focused on performing sensitivity analysis for ET0 values and the statistical adjustment of Kc -values for FAO56-ET0 with an added validation with computer simulations
Summary
Water resources are limited; the worldwide water demand is increasing with a growing population and industry [1]. Horticultural crops have a high demand for water. Crop growth and quality can only be secured by providing sufficient irrigation, especially for leafy vegetables. In this context, horticulture is forced to justify irrigation decisions, as well as optimize water use efficiency. There are several procedures available for estimating crop water requirements [3]. Irrigation scheduling based on estimating crop water requirements with reference evapotranspiration (ET0 ) and crop coefficients (Kc -values), called “crop water balance (CWB)”, is internationally well-established [4,5]. The CWB approach has been found to be simple, convenient, and reproducible for many crops in different climate conditions ([6] and the references therein). Kc -values are scaling factors generated by adjusting the measured actual crop evapotranspiration (ETc ) to a ET0 (Equation (1))
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