Biochemical Quality of Green Lettuce (Lactuca sativa L.) NFT Hydroponic in Various Types and Concentrations of Liquid Organic Fertilizer

Abstract

Green lettuce (Lactuca sativa L.) is a highly nutritious vegetable with increasing demand, making hydroponic cultivation using the nutrient film technique (NFT) a strategic option. However, reliance on AB Mix solution may lead to excessive nitrate accumulation, reducing food safety and the plant's biochemical quality. This study aimed to evaluate the effects of liquid organic fertilizer (POC) type and concentration on the chlorophyll, crude fiber, vitamin C, and nitrate content of lettuce grown hydroponically using NFT. The experiment used a split-plot design, with four POC types (Hantu, DI Grow, NASA, and Ribost) as the main-plot factor and four POC concentrations (0, 10, 20, and 30 mL/L) as the subplot factor. The experiment was replicated three times. POC concentration significantly affected chlorophyll content, with the highest value recorded at 30 mL/L (2.24 mg/L). Ribost produced the highest crude fiber content (0.97%), while DI Grow at 30 mL/L produced the highest vitamin C content (23.8 mg/100 g) and reduced nitrate levels from 3,511.0 to 2,782.1 mg/kg, below the European Union's safe threshold of 4,000 mg/kg. DI Grow at 30 mL/L is recommended as a partial substitute for AB Mix for hydroponic growers seeking to produce green lettuce with improved biochemical quality and lower nitrate levels.