Effect of Potassium Levels on Yield and Biochemical Properties of Hydroponically Grown Lettuce Varieties

Abstract

Hydroponics is an innovative alternative to traditional soil-based agriculture which addresses challenges such as soil-borne diseases and shortage of fertile land due to urbanization. Potassium is a crucial nutrient for plants influencing various physiological processes. An optimum potassium level is crop specific and dependent on various environmental factors. This study was designed to investigate the impact of potassium on yield, morphological parameters, and nutritional composition of two lettuce (Lactuca sativa) varieties; Lollo Bionda and Red Oak grown in a Nutrient Film Technique. AiGrow™ nutrient solution was formulated with four different potassium concentrations as: 300 ppm, 350 ppm, 400 ppm, and 492 ppm (control). The plants grown under each potassium condition (n=8) were tested for morphological parameters and spectrophotometric assays were conducted to analyze total protein, carbohydrate, phenol, and flavonoid contents. Compared to the control group, 300ppm group displayed the highest leaf number (30.5) and leaf area (248.9 mm2) in Red Oak. However, in Lollo Bionda the control group (492 ppm) displayed the highest leaf number (26.75), leaf area (149.49 mm2) and fresh weight (97.74 g). For Lollo Bionda, 300 ppm concentration was ideal for the highest nutritional content and 350 ppm for Red Oak. However, there were no distinctive trends observed in the biochemical parameters with increasing Potassium concentrations. Based on these results, it can be suggested that the original potassium level of 492 ppm in AiGrow™ nutrition solution can be reduced further to obtain a higher and more nutritious lettuce yield. Further research under more optimized growth conditions is required to validate these findings.