Evaluation of Lettuce Cultivars for Hydroponic Culture

Sixty cultivars of lettuce were evaluated for their performance in hydroponic culture. Seeds were germinated in Rockwool slabs and seedlings at the two true-leaf stage were anchored 6 inch apart on an NFT (nutrient film techniques) system. Plants were grown for 4 weeks with a nutrient solution containing 200 ppm N (prepared using 20-20-20 commercial analysis fertilizer). Plant growth and quality were evaluated by fresh and dry weights, plant size and shape, chlorophyll content (SPAD), soluble solids content (Brix), pH, tissue nitrate (NO₃^-), bolting, and the presence of mold and leaf margin burns. The highest fresh weight yield was obtained by Giant Caesar, followed Ansar, Coastal Star, Vivian, and Rex Rz. The total soluble solids content as measured by a refractometer was highest in 11C3487, followed by Caesar’s Favorite, Outredgeous, Balfour, and 3SX822. Tissue NO₃^- contents, which ranged from 4,000 ppm to 30,000 ppm, were lowest in Baby Romaine and Aroyo, followed by Aerostar and Encino. Refugio, Red Oak, and Four Seasons were the three cultivars that had the highest tissue nitrate contents. Cultivars with high propensity for bolting included Black Seeded Simpson, Looseleaf Blend, Arctic Crisp, Simpson Elite, and Tango. Cultivars with highest overall ratings were 11C3487, 3SX820, Vivian, Parris Island, Rex Rz, and Pomegranate Crunch.