Applicability of Partial Root-zone Irrigation model to simulate evapotranspiration and transpiration in drip irrigation jujube orchards in southern Xinjiang

Constructing a model suitable for simulating evapotranspiration and evapotranspiration components of mature jujube orchard under drip irrigation in southern Xinjiang and understanding their soil evaporation characteristics would be beneficial for growers. Based on the Shuttleworth-Wallace model and the evapotranspiration estimation model of sparse vegetation under local wet irrigation, a Partial Root-zone Irrigation model of drip irrigation for the jujube orchard was constructed. The evapotranspiration data were measured by eddy correlation methods in the jujube orchard in 2017, and the coefficients of the Shuttleworth-Wallace model and the Partial Root-zone Irrigation model of drip irrigation for jujube orchard were fitted and evaluated; the effects of the model parameters on evapotranspiration were observed by increasing and decreasing the model parameters by 10%, and the accuracy of the formulas for calculating the parameters of each model was verified. Evapotranspiration was then measured using the eddy correlation method and transpiration was measured using the liquid flow method to obtain accurate values. The reliability of the two models used to simulate evapotranspiration and transpiration in jujube orchard in 2018 were evaluated. The models were suitable for calculating evapotranspiration and evapotranspiration components in the drip irrigation jujube orchard of southern Xinjiang in 2018, as well as simulating the soil evaporation characteristics. Model coefficients of the Shuttleworth-Wallace model and Partial Root-zone Irrigation model for the drip irrigation jujube orchard were accurately fitted according to the criteria for evaluating the simulation results of the model. The results of the two models for simulating evapotranspiration were excellent for the jujube orchard in 2018, and the accuracy of the two models were the same. The results of the Partial Root-zone Irrigation model for drip irrigation jujube orchard were also good, with a difference of 15.73 mm between the model and actual measured value. It was not advisable to simulate transpiration by using the Shuttleworth-Wallace model. Therefore, the Partial Root-zone Irrigation model for drip irrigation was selected to simulate soil evaporation in the jujube orchard, and the results showed that soil evaporation accounted for 19.74% of the evapotranspiration. Thus, the Partial Root-zone Irrigation model for the drip irrigation jujube orchards can be used to accurately estimate the evapotranspiration and evapotranspiration components of the orchards.