The effect of different irrigation levels on the yield and quality of curly and head lettuce varieties grown in the greenhouse

This research was carried out in Kocaeli in the winter period of 2020-2021 in order to determine the effects of different irrigation levels on the yield and quality of some salad varieties grown in an unheated plastic covered greenhouse environment. The research was set up according to the split plot experimental design. There were three different types of curly lettuce and iceberg (Carteganas, Concorde and Melina) in the main plot, and five different irrigation levels in the sub-plots. Irrigation applications were made by drip irrigation method, taking into account the amount of water (E) evaporated from the 100 ml glass petri pot placed in the greenhouse. Taking the plant-pot coefficients (kpc) 0,25, 0,50, 0,75, 1,00 and 1,25, irrigation treatments were formed in the form of 0,25 E, 0,50 E, 0,75 E, 1,00 E and 1,25 E, respectively. During the growing season, between 32,5 mm and 122,5 mm irrigation water was applied to the experimental treatments. Head weight, head diameter and length, root length and number of leaves showed statistically significant (p<0,05) differences according to the interaction of cultivar, irrigation level and cultivar × irrigation level. The highest average head weight was obtained in Melina variety as 516,9 g, followed by Concorde and Carteganas varieties, respectively. According to the average results of irrigation levels on three different cultivars, the highest head weight was obtained from the 0.75 E as 581.2 g, while the lowest was obtained from 224,8 g and the 0,25 E. In the evaluation made in terms of cultivar × irrigation level, the highest head weight was 718,2 g and 0,75 E irrigation treatments in Melina cultivar, while the lowest 98,2 g was obtained from 0,25 E irrigation treatments in Carteganas cultivar. In other quality parameters examined, 0,75 E irrigation matter gave better results in all cultivars. The results of the research show that small petri dishes can be used in the creation of the irrigation program for the salad grown in the greenhouse in Kocaeli, and it is recommended to use 0.75 as the container coefficient.