Effects of Irrigation Water Levels on Lettuce Yield and Water Use Efficiencies under Unheated Greenhouse Conditions

This study was conducted in Meram town of Konya province under unheated greenhouse conditions in 2019 autumn (September–November) and 2020 spring (February–April) growing periods. Davidole (Lactuva sativa L. var. longifolia) curly lettuce cultivar was used as the plant material of the present study. Experiments were conducted in randomized blocks design with three replications. Irrigation levels were arranged by applying certain percentage of 4‑day cumulative evaporations from Class‑A pan (60%, 80%, 100% and 120%) and effects of irrigation treatments on yield, yield components and water use efficiencies of lettuce plants were investigated. Crop water consumptions in S60, S80, S100 and S120 treatments were respectively measured as 136.2, 149.6, 163 and 168.4 mm in 2019 and as 110.6, 123.8, 136 and 146.2 mm in 2020. In terms of commercial head weights, in 2019, the lowest value (623 g) was obtained from S60 treatment and the greatest (1130.8 g) from S120 treatment; in 2020, the lowest (900.8 g) from S60 and the greatest (1177.8 g) from S100 treatments. Water use efficiency (WUE) values varied between 38.12–55.96 kg m−3 in 2019 and between 61.65–75.24 kg m−3 in 2020. Irrigation water use efficiency (IWUE) values varied between 43.19–56.19 kg m−3 in 2019 and between 60.82–81.85 kg m−3 in 2020. Lettuce yield-response factor (ky) was calculated as 2.26 for 2019 and 0.69 for 2020. For lettuce cultivation under unheated greenhouse conditions of Konya province, S100 treatment could be recommended for autumn (September–November) productions and S80 treatment for spring (February–April) productions.