Formulation of an organic-based liquid fertilizer for hydroponic lettuce

Abstract

The consumer demand for hydroponically grown leafy vegetables has been rapidly expanding worldwide, among which lettuce is paramount. Consequently, with the escalating usage of inorganic fertilizers, adverse impacts on human health and the environment have been widely recognized. Thus, this study aimed to investigate the effect of organic-based liquid fertilizers (OBLFs) produced using agro-industrial residuals and excretory animal waste on the vegetative growth of Leaf Lettuce (Lactuca sativa L.). The Vermiwash method was employed to produce nine different OBLFs from neem leaves, gliricidia leaves, cow dung, rice husk, goat manure, banana pseudostem, poultry litter, and coconut oil cake whereas the anaerobic fermentation method was employed to produce OBLF from fish waste. The Albert’s solution, a generally utilized chemical liquid fertilizer (CLF) in commercial hydroponics was used as the control. The electrical conductivity (EC), pH, and germination percentage of OBLFs were studied. The Leaf Lettuce was cultivated in a Kratky hydroponic system containing each produced OBLF under the Completely Randomized Design (CRD). Results showed that the range of EC and pH is as follows: EC 1116.3 - 7264.6 S/cm and pH 6.5–9.5. All fertilizers except fish amino acid (FAA) had more than 80 % germination percentage, indicating non-phytotoxic characteristics in OBLFs. The rice husk-derived liquid fertilizer (RH) showed the significantly highest shoot fresh weight (75.2 g), root fresh weight (4.6 g), root dry weight (0.7 g), and maximum root length (43.8 cm) (P<0.05). The goat manure-derived liquid fertilizer (GM) showed the significantly highest shoot length (16 cm), leaf width (16.7 cm), leaf length (19.9 cm), and leaf surface area (332.6 cm2). The highest chlorophyll content was found in the CLF (18.3±4.1a µg/cm2) and RH (17.7±1.0a µg/cm2), (P>0.05). The highest number of leaves and shoot dry weight were found in the CLF (P<0.05). The best vegetative growth was obtained by the RH followed by GM in contrast to the CLF, which could be promisingly utilized in hydroponics for growing lettuce