S06 - Session O8 - Comparison of growth, phytochemical content, nutrient uptake, and water consumption of lettuce under two hydroponic system designs: nutrient film technique and deep water culture.

Authors: Teng Yang , Uttara Samarakoon *, James Altland

Two hydroponic production system designs (nutrient film technique: NFT, and deep water culture: DWC) were set up in a climate-controlled greenhouse aiming to investigate the variations of growth, nutrients and water uptake patterns, yield and quality of lettuce ( Lactuca sativa cv. Salanova Green Butter) during summer growing conditions. The research was conducted from July through August with four system replicates for each hydroponic design and each system contained nine lettuce plants. Plant photosynthetic properties, growth parameters, and irrigation solution nutrient concentrations were measured weekly. At the end of the production cycle, plants were harvested for leaf area, fresh and dry yield of shoots and roots, nutritional and phytochemical measurements, and the total nutrient consumption was calculated. Throughout the study, photosynthetic properties were higher in NFT-grown lettuce than DWC. Leaf area, fresh yield, and dry yield were higher in NFT by 13.0%, 22.8% and 27.7%. All leaf nutrients except calcium and magnesium in shoot tip were within the sufficiency range for lettuce in both systems. In the nutrient solution of both systems, nitrogen, phosphorus, and potassium concentrations decreased, while calcium, magnesium, and sulfur concentrations gradually increased during the study. There was higher percentage of nitrogen, calcium, and sulfur uptake in NFT than DWC by 9.2%, 31.4% and 33.9%. Total chlorophyll and total carotenoid concentrations in NFT-grown lettuce were lower than DWC-grown lettuce by 5.2% and 41.0%, respectively. Total water consumption was 9.6% higher in NFT than in DWC and explains the increased accumulation of some ions in NFT. In conclusion, although 30% yield increase was observed with NFT, increased total chlorophyll and total carotenoid contents were found in DWC.