Pear Tree Growth Simulation Based On Modified WOFOST Model

Pear is one of the most widely grown fruit crops in the world,with important economic and nutritional values.Predicting the yield of pear is important for regional economic development.The use of crop growth models for crop yield prediction is widely used worldwide,but most of them focus on annual crops such as wheat,cotton,rice and potato,and less research is done for fruit crops.Based on the WOFOST model,we improved the WOFOST model by introducing the real developmental phenological period of pear trees and considering the effect of summer pruning on pear trees,and calibrated and validated the model using field data to simulate the seasonal dynamic growth process of pear trees and predict the final yield.The main research findings are as follows.(1)Improvement of the WOFOST model.The simulation of pear tree growth was carried out by drawing on existing crop growth model theory and addressing pruning issues that were not considered in existing crop models.The WOFOST crop model,which has been applied for a long time and has a wide range of applications,was selected as the target model for adaptive modifications considering summer pruning.The crop growth sub-module of the WOFOST model was modified to simulate the summer pruning process by analyzing the simplified summer pruning process,mainly considering the effect of summer pruning on leaf area index(LAI)and fruit yield.(2)Calibration and validation of WOFOST model parameters.The experimental data used for calibration and validation of the improved pre-and post-WOFOST models were obtained from two pear orchards in Alar City and Awati County.Using pear growth physiological parameters collected in 2021 at the pear orchard in Alar city,the parameters of the model were calibrated using field measurements,numerical calculations and trial-and-error methods to obtain better biomass and leaf area index outputs by adjusting the input crop parameters to simulate pear growth.Data collected from pear orchards in Awati County were used to verify the simulation accuracy of the calibrated model.The results showed that the calibrated pear growth parameters had high simulation accuracy for dwarf densely planted Kullux balsam pear,and the simulation results were in good agreement with the actual values.(3)Simulation results of WOFOST model before and after improvement were compared.Before the model improvement,the accuracy of leaf area index simulation was greatly reduced after summer pruning in the first half of June because the summer pruning process could not be simulated,and the yield simulation results were also poor,and the model performance was average.The improved model was able to respond better when summer pruning occurred,and the simulation curve of leaf area index was consistent with the actual situation,and the accuracy of yield simulation results was slightly improved,and the model simulation performance was better.Indicating that the R~2 values of TWSO ranged from 0.899 to0.976,and the R~2 values of LAI ranged from 0.849 to 0.924.The modified model also showed high accuracy,with a normalized root mean square error(NRMSE)ranging from 12.19%to 26.11%for TWSO,and the NRMSE values for LAI were less than 10%.The modified model also had a good simulation performance for the soil moisture(SM)under all eight pruning intensity treatments,showing good agreement(0.703≤R~2≤0.878)and low error(NRMSE≤7.47%).Therefore,the improved model can simulate the summer pruning process,and the simulation results are closer to the actual pear tree growth situation of pear orchard management.(4)The effect of different pruning intensity on the growth and yield of pear trees.The same pruning intensity gradient settings were carried out in two pear orchards.The experimental results showed that the leaf area index of the two pear orchards under different summer pruning intensities tended to decrease with the increase of pruning intensity,the yield of pear trees first increased and then decreased with the increase of pruning intensity.The highest yield of pear trees was achieved when the pruning intensity was about 20%,and the total dry matter decreased with the increase of pruning intensity.The model simulation results were consistent with the actual measurement data and observation results.