Evapotranspiration of grapefruit in the eastern Mediterranean region of Turkey

Abstract

Different pan coefficients ( k 1 = 0.6 and k 2 = 1.0) and irrigation intervals ( I 1 = 15 and I 2 = 25 days) were used in this study. The average total evapotranspiration ( E t) was 1039 mm (for I 1 k 2) and 988 mm (for I 2 k 2). Effective root depth of grapefruit varied from 90 to 110 cm depending on the irrigation intervals. Calculated pan coefficients ( Et Eo ) reached a maximum value of 1.2 in treatment I 1 k 2 in spring and winter owing to the contribution of higher rainfall. However, calculated coefficients in the irrigation season were lower than the ones applied in this study. There were no significantly different effects of irrigation treatments on the yields of grapefruit, but the yield from irrigation interval of 15 days was slightly higher. In periodicity years, yields and the number of fruits decreased by 52-45% and 85-77% with respect to the irrigation treatments. In years of normal yield, the average fruit weight was about 32% lower and seed number was two to four times higher than in periodicity years. In years of normal yield, water use efficiency (WUE) was highest in treatment I 1 k 1. Overall and irrigation WUE values decreased by 51% and 46% in periodicity years, respectively.