The effects of dififerent irrigation regimes on cucumber (Cucumbis sativus L.) yield and yield characteristics under open field conditions

A study was conducted to determine the effects of different drip irrigation regimes on yield and yield components of cucumber (Cucumbis sativus L.) and to determine a threshold value for crop water stress index (CWSI) based on irrigation programming. Four different irrigation treatments as 50 (T-50), 75 (T-75), 100 (T-100) and 125% (T-125) of irrigation water applied/cumulative pan evaporation (IW/CPE) ratio with 3-day-period were studied. Seasonal crop evapotranspiration (ETc) values were 633, 740, 815 and 903 mm in the 1st year and were 679, 777, 875 and 990 mm in the 2nd year for T-50, T-75, T-100 and T-125, respectively. Seasonal irrigation water amounts were 542, 677, 813 and 949 mm in 2002 and 576, 725, 875 and 1025 rum in 2003, respectively. Maximum marketable fruit yield was from T-100 treatment with 76.65 t ha(-1) in 2002 and 68.13 t ha(-1) in 2003. Fruit yield was reduced significantly, as irrigation rate was decreased. The water use efficiency (WUE) ranged from 7.37 to 9.40 kg m(-3) and 6.32 to 7.79 kg m(-3) in 2002 and 2003, respectively, while irrigation water use efficiencies (IWUE) were between 7.02 and 9.93 kg m(-3) in 2002 and between 6.11 and 8.82 kg m(-3) in 2003. When the irrigation rate was decreased, crop transpiration rate decreased as well resulting in increased crop canopy temperatures and CWSI values and resulted in reduced yield. The results indicated that a seasonal mean CWSI value of 0.20 would result in decreased yield. Therefore, a CWSI = 0.20 could be taken as a threshold value to start irrigation for cucumber grown in open field under semi-arid conditions. Results of this study demonstrate that 1.00 IW/CPE water applications by a drip system in a 3-day irrigation frequency would be optimal for growth in semiarid regions. (c) 2004 Elsevier B.V. All rights reserved.