Long-term field experiments were carried out between 1985 and 1988 to determine the effect of different irrigation intervals and pan coefficients on the fruit and trunk growth rates and yield of mature grapefruit trees grown in the Eastern Mediterranean Region of Turkey in a medium-light textured soil. | Tr. J. of Agriculture and Forestry 23 (1999) 401-411 © TÜBİTAK Effects of Different Irrigation Programs on Fruit, Trunk Growth Rates, Quality and Yield of Grapefruit Trees Rıza KANBER, Harun KÖKSAL, Attila YAZAR, Bülent ÖZEKİCİ, Sermet ÖNDER Department of Agricultural Structure and Irrigation Department, Faculty of Agriculture, University of Çukurova, Adana-TURKEY Received: Abstract: Long-term field experiments were carried out between 1985 and 1988 to determine the effect of different irrigation intervals and pan coefficients on the fruit and trunk growth rates and yield of mature grapefruit trees grown in the Eastern Mediterranean Region of Turkey in a medium-light textured soil. Two different irrigation intervals (I1=15 and I2=25 days), and pan coefficients (k1= and k2=) were used. Higher evapotranspiration values were obtained from the treatments with k2 coefficient in the two irrigation regimes. The average irrigation water (IR) and evapotranspiration (Et) values were 796 mm and 1039 mm for I1k2, and 782 mm and 988 mm for I2k2, respectively. The grapefruit trees exhibited periodicity during the period of study. Results indicate that the effects of the irrigaiton programs on grapefruit yield were not significantly different. However, slightly higher yields were obtained from the frequently irrigated trees with an average of ± t/ha for I1k1. In periodicity years, the yield and the number of fruits harvested decreased by 45-52% and 77-85% with respect to irrigation treatments. In normal-yield years, the average fruit weight and diameter were nearly 32% and 20% lower than in the periodicity years, and the seed number was two to four times greater than in the periodicity years. It was found that there was an inverse relationship between fruit extract and TSS (total soluble solid percentage). The fruit extract content increased to , whereas TSS decreased to in normal-yield years. Fruit extract and peel thickness varied during
