Determination of Water Requirement, Single and Dual Crop Coefficients of Garlic in Cold Semi-Arid Climate

This study was carried out to determine water requirement and crop coefficients of garlic (Allium sativum L.) at the climatic station of the Agricultural Faculty of Bu-AliSina University، Hamedan. Daily crop evapotranspiration (ETC) during growing season varied from 0. 1 to 11. 22 mmd-1. Garlic water requirement during growing season under full water availability was 546. 5 mm with a water use efficiency of 2. 85 g/kg of evapotranspiration. Crop coefficients at initial، developing، and final growth stages were 0. 5، 1. 4 and 0. 3، respectively. Based on the models recommended by FAO56، single and dual crop coefficients were also determined. In order to predict garlic evapotranspiration from the climatic data، multiple regression models were applied. Results showed that predicted ETC by employing dual crop coefficients produced smaller difference comparing to the lysimeter measured ETC (RMSE=2. 46 mmd-1). Considering ETC computation procedures and time required، single crop coefficient was much simpler than dual crop coefficient.