The effects of drip line depths and irrigation levels on yield, quality and water use characteristics of lettuce under greenhouse condition
This study was conducted to investigate the effects of different drip irrigation methods and different irrigation levels on yield, quality and water use characteristics of lettuce (Lactuca sativa var. longifolia cv. Lital) cultivated in a solar greenhouse from 07 October 2009 to 03 December 2009 in the Eastern Mediterranean region of Turkey. The irrigation methods were consisted of traditional surface drip irrigation (TDI), subsurface drip irrigation at 10 cm drip line depth (SDI10) and subsurface drip irrigation at 20 cm drip line depth (SDI20). At the treatment of irrigation levels, five irrigation treatments (I) were based on adjustment coefficients (0.25, 0.50, 0.75, 1.0 and 1.25) of Class A pan evaporation. For the yield and quality parameters of plant; marketable head weight (yield), number of marketable leaves, leaf area, plant height and diameters, plant dry weight, core diameters and firmness of head, leaf chlorophyll content, total soluble solids (TSS as °Brix), electrical conductivity (EC), pH, total dissolved solids (TDS) and salinity of leaves’ juice were determined. The yield and yield components were not affected by the irrigation methods except for core and plant diameters. Irrigation levels had significantly (p < 0.01) different effects on yield and yield components except for plant dry weight, plant height and head firmness. The results showed that the highest yield was obtained from SDI10xI100 treatment. The water use efficiency (WUE) and the irrigation water use efficiency (IWUE) increased as the irrigation was reduced.
Key words: Subsurface drip irrigation, irrigation level, water use efficiency.