Analysis of nutrient composition of liquid organic fertilizer for optimizing fertilizer dosing for hydroponic crop production

Authors: CHOWDHURY, MILON - Kentucky State University; SAMARAKOON, UTTARA - The Ohio State University; Altland, James

Submitted to: Acta horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2023
Publication Date: 5/1/2025
Citation: Chowdhury, M., Samarakoon, U., Altland, J.E. 2025. Analysis of nutrient composition of liquid organic fertilizer for optimizing fertilizer dosing for hydroponic crop production. Acta horticulturae. Article 1428. https://doi.org/10.17660/actahortic.2025.1428.3.
DOI: https://doi.org/10.17660/actahortic.2025.1428.3

Interpretive Summary: This study addressed the challenge of optimizing nutrient dosing for hydroponic crop production using liquid organic fertilizers, which are increasingly adopted due to environmental and economic benefits. Few studies have been conducted on the application of organic fertilizers in hydroponic systems, leading to uncertainties in their nutrient composition and effectiveness. The accomplishment of the study was the comprehensive analysis of nutrient compositions of various commercial liquid organic fertilizers, including Grow Big, Espartan, Caos, Bombardier, Tomato & Veg formula, and Pre-Empt, which were diluted according to manufacturer recommendations and compared to synthetic fertilizers. It was found that no liquid organic fertilizer matched the exact nutrient ion ratios of standard synthetic fertilizers, but Grow Big, Espartan, and Pre-Empt had the closest compositions for leafy greens and high-wire crop production. This research provides growers with valuable information to select appropriate fertilizers and prepare target concentrations from the tank-mixing stage to dosing, thereby improving the efficiency and effectiveness of organic hydroponic crop production.

Technical Abstract: Environmental awareness and economic benefits are encouraging growers in controlled environment agriculture (CEA) to adopt organic growing media and fertilizers. However, few studies have been conducted regarding the application of liquid organic fertilizer for hydroponic crop cultivation. The current study aimed to survey and select commercial liquid organic fertilizers and analyze their nutrient composition for optimizing nutrient dosing. First, liquid organic fertilizers certified by the organic materials review institute (OMRI) were identified based on the listed nutrient profile and reports of other studies. The selected liquid organic fertilizers (i.e., Grow Big, Espartan, Caos, Bombardier, Tomato & Veg formula, Pre-Empt) were diluted according to the manufacturer’s recommended rate. Physical changes, such as biofilm accumulation or sedimentation, and chemical composition were checked at two-week intervals after preparation. Synthetic fertilizers for hydroponic substrate-based and liquid cultures were considered as the control. The identified nutrient composition was compared to the standard synthetic fertilizer recipe to assess the nutrient dosing for organic leafy greens and high-wire crop production. The concentration (ppm) of macronutrients (N, P, K, Ca, Mg, S), total nitrogen (TN), and organic carbon (OC) of each sample were measured. After two weeks of dilution, biofilm accumulation, sedimentation, and fermentation were observed in some liquid organic fertilizers, which might be solved by sanitization or aeration. The electrical conductivity (EC) of the diluted fertilizers was within the range of 1.5 to 2.0 mS cm-1, except for Espartan (0.69) and Bombardier (0.88). The pH was between 5.3 to 6.8, except for Caos (7.3). The total nitrogen concentration was above 100 ppm in Grow Big, Bombardier, and Pre-Empt and below in Espartan, Caos, and Tomato & Veg formula. A comparison of nutrient components between synthetic and organic fertilizers indicated that no liquid organic fertilizer matched the exact ratio of nutrient ions in standard synthetic fertilizer recipes. However, Grow Big, Espartan, and Pre-Empt had the closest composition to synthetic fertilizer used for leafy greens and high-wire crop production. This research will help growers select fertilizers and prepare target concentrations of liquid organic fertilizers from the tank-mixing stage to dosin