Vol. 9, Special Issue 12, Part J (2025)

Salinity plays a crucial role in hydroponics as it influences water uptake, nutrient availability, and overall plant health. Excessive salinity can lead to osmotic stress, reducing plant growth, while optimal levels support nutrient absorption. Similarly, the choice of rooting substrate affects root aeration, moisture retention, and nutrient accessibility, all of which are essential for plant development. A field experiment was conducted during the Rabi season of 2019 at ZARS, V.C. Farm, Mandya, to evaluate the effects of salinity levels and rooting substrates on the growth and yield of lettuce in a hydroponic system. The experiment utilized a Randomized Complete Block Design with a 4 × 4 factorial arrangement, testing four nutrient solution salinity levels (0.5, 0.75, 1.10, and 1.30 dS m⁻¹) and four rooting substrates (Rockwool, sponge, sphagnum moss, and floral bed). These factors were selected to examine their combined influence on plant growth, as salinity affects nutrient uptake and osmotic balance, while substrate properties play a crucial role in root development. The study comprised 16 treatment combinations, each replicated twice. The results revealed that salinity levels, rooting substrates and their interaction recorded non-significant in primary (N, P and K), secondary (Ca, Mg and S) and micronutrient (Fe, Cu, Mn and Zn) content. The nutrient solution with salinity level of 1.30 dS m-1 with Rockwool rooting substrate recorded significantly higher nutrient uptake followed by sphagnum moss on par with sponge and lower uptake was noticed in floral bed in lettuce compared to other treatment combination. These findings indicate that hydroponic lettuce can tolerate a range of salinity levels without major disruptions to nutrient balance. However, selecting the right substrate is crucial for maximizing nutrient uptake and overall plant health. The results provide valuable insights for optimizing hydroponic nutrient management strategies, supporting more efficient and productive lettuce cultivation.