The combined effect of irrigation regimes, fertilization and Tween 20 treatments on lettuce crop yield under greenhouse conditions

A pot experiment was conducted in a 20 m² sealed plastic greenhouse at a specialized farm in Santa Center, Gharbia Governorate, Egypt, during the 2021–2022 winter season. The study assessed the combined effects of three irrigation levels, two fertilization rates, and two Tween 20 treatments on lettuce (Lactuca sativa L.) growth, photosynthetic pigments, and NPK %. Results showed that the combination of (I₂×F₁×T₁) significantly enhanced plant fresh weight (753.3 g), dry weight (48.5 g), shoot dry weight (21.9 g), fresh root weight (85.5 g), dry root weight (26.6 g), and root length (18.0 cm). The plant height (39.7 cm) and the highest Number of leaves/plant (49 leaves/plant) were observed under I₁×F₁×T₁. The I₁×F₁×T₁ treatment also resulted in the highest: N% (3.39%), P% (0.330%), and K% (3.91%). Conversely, the lowest performance was recorded under I₃×F₂×T₂. Significant interactions among the three factors were noted in chlorophyll and carotenoid contents, with I₂×F₂×T₂ producing the highest pigment levels, indicating enhanced photoprotection. These findings highlight the value of customized input management to support sustainable and efficient lettuce production in water-scarce environments.