The southeastern U.S. struggles with horticultural production due to a harsh climate that exacerbates issues such as severe weed, soil-borne pests, and diseases. Hydroponic cultivation offers a promising solution by reducing pesticide use and facilitating year-round production. However, there is a lack of regionally research-based guidance on hydroponic cultivation in Mississippi. This study aimed to screen the lettuce cultivars that are suitable for hydroponic cultivation in Mississippi and to evaluate the effects of different hydroponic systems and biostimulants on plant growth. Six lettuce cultivars (Buttercrunch, Adriana, Rex, Rouxai, Oscarde, and Skyphos) were grown in two hydroponic systems (vertical tower and deep-water culture), and subjected to three biostimulant treatments (control, kelp and microbial biostimulant) to assess their impacts on growth parameters. Results indicated that lettuce cultivar significantly affected hydroponic lettuce growth. Adriana showed the highest leaf area and plant biomass while Buttercrunch displayed the highest relative chlorophyll content (SPAD) and shoot fresh weight. Rouxai accumulated the least biomass. Biostimulants demonstrated positive effects on lettuce plant growth; however, their efficacy was specific to both the hydroponic system and lettuce cultivar. Kelp was found to be more effective than microbial biostimulants in enhancing growth parameters. Overall, lettuce plants grown in the deep-water culture system exhibited faster growth compared to those in the vertical tower system. In conclusion, this study demonstrated that hydroponic cultivation is a viable solution for lettuce production in Mississippi, with deep-water culture system and kelp biostimulant significantly enhancing growth parameters.
