The Effects of Different Irrigation Levels on the Yield and Physical Properties of Lettuce Cultivars (Lactuca sativa var.campania)

This study was carried out to investigate the effects of different water levels on the yield and physical properties of Lettuce cultivars (Lactuca Sativa var.campania), grown in unheated greenhouse at the research center of Canakkale Onsekiz Mart University in 2011and 2012, in Turkey. The research was designed to randomised coplete block design. The amount of irrigation water was determined through measuring evaporation from Class–A pan and Crop–pan coefficients (Kcp) were 0.25, 0.50, 0.75, 1.0 and 1.25.Therefore, the level of irrigation water in treatments was arranged according to the coefficients of Kcp, as follows; 25% (I0.25), 50% (I0.50) , 75% (I0.75) , 100% (I1.00) , 125% (I1.25) . Two crop production was carried out during winter time. In first growing period, the amount of irrigation water applied changed from 15 mm to 75 mm and in the second production period, it was from 9 to 45 mm, and in the first and second growing period, evapotranspiration was between 88 mm and 115 mm and from 56 to 79 mm, respectively. The increment of the amount of irrigation water has the positive effect on the yield, and it fluctuated the yield, in turn, between 2239 and 3742 kg/da –1 in two growing periods. In both growing periods, the highest irrigation water in teratments of I1.00 and I1.25 increased the yield of lettuce and also leaf area was within the highest rank group as an a in these treatments, and other treatments (I0.25, I0.50 and I0.75) took place in second group as b. Among groups, while having significant differences in canopy diameter there was no differences in canopy height. Class–A pan can be used in irrigation water management successfully and to use 1.25 for Kcp for lettuce in an unheated greenhouse gives the highest yield. Hence, this result can be considered as a strategy for water management in lettuce grown in an unheated greenhouse.