Short communication. Effect of deficit irrigation on curly lettuce grown under semiarid conditions

Field experiments were conducted to characterize the effects of deficit irrigation on curly lettuce (Lactuca sativa var. Crispa cv. Bohemia) evapotranspiration, water use efficiency, marketable yield, yield components and mineral contents. The experiments were performed under semiarid climatic conditions in Erzurum province (east of Turkey) in the summer periods of 2005 and 2006. Irrigation water levels were selected to be 100% of usable soil water in full irrigation treatment (control) (T-100) and 80%, 60%, 40% and 20% of usable soil water in deficit irrigation treatments (T-80, T-60, T-40 and T-20, respectively). Average seasonal evapotranspiration was 232 mm in T-100 and 121 mm in T-20. Average marketable yield was 39.49 Mg ha(-1) in T-100 and 14.57 Mg ha-1 in T-20. A linear relationship (y=0.23x-13.97; R-2=0.94) was found between seasonal evapotranspiration (x) and marketable plant yield (y). According to the regression equation, the yield response factor (k(y)) was found to be 1.39, and the coefficient of determination 0.91. Average water use efficiency was 168.88 kg ha(-1) mm(-1) in T-100 and 117.39 kg ha(-1) mm(-1) in T-20. The lowest plant length, width, steam diameter, leaf number, macro and micro elernent content values were obtained for T-20 in both years.