Although, as compared to other crop models, AquaCrop has a significantly smaller number of parameters and a better balance between simplicity, accuracy and robustness, AquaCrop model is not yet available for fruit trees. So, AquaCrop model was studied and modified to suit the deciduous fruit trees such as peaches under drip irrigation system and the conditions of light soil in the arid and semi arid climate. The modified model is able to simulate the growth cycle of the deciduous fruit trees and estimate the yield under different stress condition. After that, a computer program was planned and developed with easy interface and few requirements to estimate the resulting yield by means of yield response factors under different stress condition. To validate the simulation program, two seasons experiment were designed to determine the yield for peach trees (Prunus persica) which is as an example of a deciduous tree, under water stress conditions by two different techniques Partial root-zone drying (PRD) and Regulated deficit irrigation (RDI) in the west noubaria rural development project research station. PRD and RDI are examples of new water-saving irrigation strategies used for reducing applied irrigation water. These techniques have been successfully adopted to produce many crop and fruit species and improve the water use efficiency. The validation of simulation program was performed using the results of an experiment peach field in 2011 and 2012 seasons. The simulated yield was close to those measured; with index of agreement (d) and correlation coefficient (r) were close to 1 in both seasons. Also, the simulation program was tested to simulate the peach fruit yield under different irrigation deficit percentages
Also, the simulation program was tested to simulate the peach fruit yield under different irrigation deficit percentages using PRD and RDI techniques, 100 % to 30% of the irrigation control treatment water volume, during the slow fruit growth phase until the maturity. Yield response factor corresponding to the levels of shortage of irrigation water was determined in RDI and PRD strategy, were 1.32 and 0.72, respectively.