Investigation of water requirement system in determining the actual amount of irrigation water of peanut plant based on inverse solution of yield function under water stress conditions

Estimating water requirement and determining the actual amount of water is one of the most important factors in the management of agricultural water resources and one of the requirements of any irrigation project. The present study was conducted to investigate the water requirement system in determining the actual amount of peanut irrigation water based on the inverse solution of yield function under water stress in two crop years 2017 and 2018 in Guilan province. The experimental design was performed in the form of split plots in a randomized complete block design with three replications. The main factor of irrigation management included rainfed and 40, 60, 80, 100% Water requirement supply and sub treatment included two cultivars of peanut Guil and Jonobi. The results showed that the highest evapotranspiration in supplying 100% of water requirement in 2017 and 2018 was 446.7 and 524.1 mm in the Jonobi cultivar and 438.5 and 521.9 mm in the Guil cultivar, respectively. in the measured and estimated values of irrigation need by the water requirement system, the values of the coefficient of determination in the Jonobi and Guil cultivars are 0.65 and 0.64 respectively, and the root mean square error for Jonobi and Guil cultivars were 52.60 and 52.24, respectively, and the mean error deviation was 15.53 and 15.03, respectively. The agreement Wilmot index and efficiency coefficient of the model in 2017 and 2018 were 0.95 and 0.75 for the Jonobi cultivar and 0.95 and 0.76 for the Guil cultivar, respectively. According to the available results and statistical indicators, the water demand system provided a reasonable estimate of the actual amount of irrigation water in two peanut cultivars.