This study was conducted to investigate the effects of drip irrigation on yield and yield components of watermelon [Citrullus lanatus (Thunb.) Crimson Tide F1] under semiarid conditions in the Southeastern Anatolian Project Region, Harran Plain, Şanlıurfa, Turkey, during 2002 and 2003. Using a 4-day irrigation period, 4 different irrigation regimes were applied as ratios of irrigation water/cumulative pan evaporation (IW/CPE): 1.25 (I125), 1.00 (I100), 0.75 (I75), and 0.50 (I50). Seasonal crop evapotranspiration (ETc) rates were 720, 677, 554, and 449 mm in the first year and 677, 617, 519, and 417 mm in the second year for irrigation treatments I125, I100, I75, and I50, respectively. Amounts of irrigation water applied to the 4 respective treatments were 764, 642, 520, and 398 mm in 2002 and 709, 591, 473, and 355 mm in 2003. Maximum yield was obtained from I125, with 84.1 t/ha in 2002 and 88.6 t/ha in 2003. Yield was reduced significantly as the irrigation water was reduced. The values of water use efficiency ranged from 9.6 to 11.7 kg/m3 in 2002 and 10.8 to 13.1 kg/m3 in 2003. The unstressed I125 treatment produced 10.1 kg marketable watermelons/m3 irrigation in 2002, and 11.3 kg/m3 in 2003. By comparison, the least irrigated (I50) treatment produced 12.4 kg/m3 in 2002, and 14.9 kg/m3 in 2003. A yield response factor (ky) value of 1.15 was determined based on averages of 2 years, and watermelon was found to be sensitive to water stress. This result showed that yield loss (1 – Ya/Ym) is more important than evapotranspiration deficit (1 – ETa/ETm). The study demonstrates that 1.25 IW/CPE water applications by a drip system in a 4-day irrigation frequency might be optimal for watermelon grown in semi-arid regions similar to those in which the work was conducted.
Assessing Growth and Water Productivity for Drip-Irrigated Maize under High Plant Density in Arid to Semi-Humid Climates
