Growth and Yield Response of Red Leaf Lettuce (Lactuca sativa L. cv. Merlot) Substituted with Seaweed Extract as Hydroponic Nutrient Solution

Abstract

The increasing prices of chemical-based hydroponic nutrient solutions (CHNS) in the market have led to replace a percentage of its recommended rate with available local biostimulants to save hydroponic solution costs. Thus, a study on hydroponics utilizing different concentrations of Eucheuma cottonii seaweed extracts (SWE) as a biostimulant was conducted to determine the growth and yield of red leaf lettuce. The various concentrations of seaweed extract are a percentage substitution of CHNS. The treatments are 100% CHNS, 25% SWE + 75% CHNS, 50% SWE + 50% CHNS, and 75% SWE + 25% CHNS. The plant height of red leaf lettuce under 50% SWE (10.65 cm) is the highest compared to the lettuce grown under 100% CHNS (9.81 cm) and 75% SWE (9.76 cm) one week after treatment application. There was no significant difference in the plant height observed weeks after one week from treatment application. There was no significant difference among treatments on the number of leaves. The leaf width (12.28 cm) and plant weight (28.91 g) of red leaf lettuce under 25% SWE are comparable to the lettuce plant under 100% CHNS (11.47 cm, 33.62 g, respectively). The leaf length, conversely, is the highest at 75% SWE (12.69 cm). Similar growth had been observed among treatments used in the root length and dry weight. Thus, the commercial hydroponic nutrient solution could only be replaced up to 25% with seaweed extract without any significant reduction in growth and yield in lettuce except for plant height and leaf length.