Irrigation scheduling based on pan evaporation values for cucumber (Cucumis sativus L.) grown under field conditions Ahmet Ertek a, * , Suat S ¸ensoy b ,I ˙ brahim Gedik c , Cenk Ku ¨c ¸u ¨kyumuk c a Faculty of Agriculture, Department of Irrigation and Drainage, Su ¨leyman Demirel University, 32260 Isparta, Turkey b Faculty of Agriculture, Department of Horticulture, Yu ¨zu ¨ncu ¨ Yıl University, 65080 Van, Turkey c Department of Irrigation and Drainage, Yu ¨zu ¨ncu ¨ Yıl University, 65080 Van, Turkey Accepted 24 March 2005 Available online 26 April 2005 Abstract This study was conducted to determine the most suitable irrigation frequency and quantity in cucumber grown under field conditions. The amount of water used was based on pan evaporation from a screened Class-A pan. Irrigation treatments consisted of two irrigation intervals (I1: 4 and I2: 8 day), and three plant-pan coefficients (K cp 1: 0.50; K cp 2: 0.75 and K cp 3: 1.00). Plants were first watered at the transplanting date and scheduled irrigations were initiated after 4- and 8-day intervals. Irrigation quantities applied to the treatments varied from 320 to 509 mm; seasonal plant water comsumption or evapotranspiration of irrigation treatments varied from 391 to 597 mm; and the cuccumber yield varied from 17.99 to 45.20 ton ha 1 . The highest total yield was obtained from I2K cp 3 treatment. Moreover, K cp 3 treatments had the highest early yield. E t /E pan ratio according to treatments ranged from 0.29 to 1.25. Irrigation treatments had significant effects (P < 0.01) on yield and there were significant positive linear relations (P < 0.01) between the fruit number and irrigation water and between the plant water compsumption and the yield. In conclusion, K cp 3 treatment with 8-day-irrigation interval is recommended for cucumber grown under field conditions in order to get higher cucumber yield and to save time and labor. Furthermore, www.elsevier.com/locate/agwat Agricultural Water Management 81 (2006) 159–172 * Corresponding author. Tel.: +90 246 2111395; fax: +90 246 2371693. E-mail address: aertek25@operamail.com (A. Ertek). 0378-3774/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.agwat.2005.03.008