Evaluation of ET models to study water requirement of Pomegranate (Punica granatumL.)for Satara district of Maharashtra

The study was carried out to select the best model for the estimation of reference crop evapotranspiration (ET_r), develop crop coefficient (K_cp) and estimate pomegranate evapotranspiration (ET_p) for Satara district (North latitude 17⁰42^’and East longitude 74⁰ 01^’at 660.00 m amsl) in semi-arid region of Maharashtra. Six most commonly used reference crop evapotranspiration models were selected for estimating the ET_r. Out of these six models, P-M model was consideredas the most appropriate as found from the literature and ET_r of the other models were compared with ET_r of P-M to select the best model from remaining five. The present study is based on analysis on long term (34 years) climatic data and measured shaded area at solar noon hour for 1^st to 5^th year pomegranate orchards. The values of ET_r estimated by Radiation model were found higher followed by modified Penman, Blanney-Criddle, Pan Evaporation, Hargraeves-Samani and Penman-Monteith models. The different models were compared with P-M model on the basis of the least root mean square error (RMSE) and regression analysis. Out of five models, Hargreaves-Samani model gave the least value of root mean square error. The measured shaded area increased from new leaf initiation to maturity of crop ranging from 0.46 to 10.62 m² and decreased from harvesting periods from 10.62 to 5.44 m². The crop coefficient values ranged from 0.15 to 1.18 and pomegranate ET ranged from 0.37 to 3.26 mm from new leaf initiation to maturity period. The seasonal values of water to be applied ranged from 1015.0 to 1199.9, 2338.40 to 2808.10, 6430.10 to 7681.40, 9041.30 to 11850.80 and 11766.10 to 13991.10 Lyr⁻¹tr⁻¹ respectively, for 1^st to 5^th year pomegranate tree.