Simulating on the effects of irrigation on jujube tree growth, evapotranspiration and water use based on crop growth model

Jujube is an excellent fruit crop with important economic and ecological benefits in arid regions. With the shortage of water resources, quantifying the jujube tree growth response to irrigation is significant for improving water use efficiency (WUE) and establishing adequate water management strategies. However, most studies on water management for jujube tree are based on statistical analysis of field trials to determine irrigation strategies, and few studies focus on using crop growth simulation methods to quantitatively analyze the impact of water management on jujube growth and WUE. Therefore, the research aimed at evaluating the ability of a calibrated WOFSOT (WOrld FOod Studies) model to simulate seasonal jujube tree development dynamics and water movement, and to quantitatively describe the influence of different irrigation treatments on yield, evapotranspiration and WUE. Simulated seasonal growth dynamics for total dry weight of stems, leaves and fruits (TAGP) and leaf area index (LAI) agreed well with field-measured values at each irrigation treatment in 2016 and 2017, showing R-2 values from 0.92 to 0.98 for TAGP, 0.79 to 0.97 for LAI, with high accuracy (8.7 % <= NRMSE <= 20.5 % for TAGP, 8.1 % <= NRMSE <= 21.1 % for LAI). The calibrated model had also high global simulation performance of soil water balance process for all five irrigation treatments, showing good agreement (R-2 >= 0.78) and low error (NRMSE <= 6.6 %). Simulated yield, actual evapotranspiration (ETa) and WUE in two orchards with different field capacity (FC) have also been confirmed to hold good agreement and high accuracy, and their R-2 and NRMSE were 0.93 and 8.5 %, 0.80 and 3.6 %, 0.85 and 10.4 % at FC = 0.296 cm(3) cm(-3), 0.86 and 10 %, 0.62 and 5.8 %, 0.90 and 9.4 % at FC = 0.194 cm(3) cm(-3), respectively. In summary, the proposed method can quantitatively describe the impact of irrigation strategies on jujube tree seasonal growth dynamics, yield, evapotranspiration and WUE, which may become a promising quantitative analysis method for the coupled effects of soil, meteorology, water management and jujube tree growth, and decision-making for irrigation strategies.