Watercress (Nasturtium officinale L.) is a leafy green vegetable, that is a member of the Brassicaceae family. It provides a rich and bioavailable source of vitamin C, significantly higher than many fruits and vegetables, including oranges. Vitamin C is associated with numerous health benefits, such as antioxidant protection, immune system support, enhanced collagen production, improved iron absorption, improved eye health and lowered risks of chronic diseases such as cardiovascular disease and cancer. Thus, consuming adequate amounts of vitamin C daily is important for human health. A 100g of watercress provides 62mg (103% Recommended Dietary Allowance) of vitamin C. In humans, vitamin C takes part in various physiological processes; however, due to the functional loss of the gene coding for L-gulonolactone oxidase, humans cannot synthesize vitamin C and must rely primarily on plant-based foods for their needs. For this reason, increasing the vitamin C content of crops is essential for supporting human health. Some studies have shown potential effects of fertilization, particularly magnesium fertilization on vitamin C content. Therefore, this study aims to contribute to optimization of nutrient management in hydroponics to enhance nutritional value. The research was conducted using a split-plot design. Four magnesium fertilization rates (100 mg/l, 150 mg/l, 200 mg/l and 250 mg/l) were applied to watercress in Nutrient Film Technique (NFT) hydroponic system under controlled environment, ensuring desirable nutrient application, temperature, light, pH and electrical conductivity. Spectrophotometric methods were used to quantify Vitamin C. The preliminary findings indicate an increase in Vitamin C content with an increase in magnesium application rates, with the highest rate maximizing its accumulation. These results contribute to understanding the effects of magnesium fertilization on vitamin C synthesis in watercress and will help guide farmers and producers in optimizing vitamin C content during production to support human dietary needs and health. Keywords: Watercress, Vitamin C, Magnesium Fertilization, Hydroponics, Nutrient Optimization
