Journal of Agricultural, Life and Environmental Sciences ISSN:2233-8322(Print) 2508-870X(Online)

The results of testing the applicability of pig manure-fermented liquid fertilizer (PMLF) for hydroponic lettuce cultivation showed that the growth and yield of lettuce were very low compared to those of normal nutrient solutions for hydroponics. Compared with the nutrient solution for the hydroponics of lettuce (NSHL), the ion content of PMLF was lower in nitrate nitrogen, phosphorus, calcium, magnesium, and sulfur but ammonia nitrogen, potassium, sodium, and chlorine were higher. In particular, the sodium and chlorine contents of PMLF were 8.9 and 27.2 times higher than those of NSHL, respectively. After 14 days of treatment, the NO₃^-N, NH₄⁺-N, PO₄^2-P, and Ca²⁺ ion contents of the drained nutrient solution decreased rapidly, resulting in an insufficient supply of nutrients. The yield of PMLF is thought to be low because of lack of certain nutrients and nutrient imbalances. In this study, heavy metal contents within the plant, such as Cd, Ni, As, and Pb, were not detected in any of the treatments, and the detected amounts of Cu and Zn were lower than the acceptance criteria. The total polyphenol and flavonoid contents in the PMLF group were higher than those in the NSHL group. In addition, the oxygen-scavenging ability of ABTS in the PMLF treatment was higher than that in NSHL. These results confirmed that it is possible to produce high-quality lettuce with excellent antioxidant ability when hydroponic lettuce is grown using organic NSHL. These results confirmed the possibility of producing lettuce with high antioxidant capacity when organic PMLF was used in hydroponic lettuce cultivation; however, there were also problems with lettuce growth inhibition and low yield due to nutrient imbalance. In addition to supplementing and supplying insufficient nutrients, complementary research, such as the effect of sodium and chlorine accumulation in the medium on lettuce growth, should be continuously pursued.