Utilization of Tofu Industry Effluent as Liquid Organic Fertilizer: Effects on Growth Performance of Brassica rapa L (Pokcoy)

Abstract

Background: The nutrient-rich wastewater from household-scale tofu production is a sustainable and readily available resource with great potential as liquid organic fertilizer (LOF). This study focuses on valorizing tofu effluent for sustainable crop cultivation, with novelty in identifying the optimal dilution that maximizes Brassica rapa L. (pakcoy) growth while maintaining environmental safety. Objective: This study aimed to evaluate the feasibility of tofu wastewater as a raw material for LOF production and to determine the most effective dilution for improving plant growth and physiological responses. Methods: The experiment employed a Completely Randomized Design (CRD) with four LOF concentrations (0%, 10%, 25%, and 50%) applied to soil media for four weeks. Plant height, leaf number, fresh and dry weight, and protein content were recorded weekly and analyzed using two-way ANOVA, Tukey’s HSD, and polynomial regression to evaluate treatment effects and dose–response trends.  Results: LOF concentration, observation time, and their interaction showed highly significant effects (p < 0.0001) on all measured parameters. Treatments with 10% and 25% LOF markedly enhanced plant growth, particularly in the third and fourth weeks. Polynomial regression revealed a nonlinear dose–response pattern, with 10% optimal for early growth and 25% yielding the highest biomass and protein content, whereas 50% caused nutrient oversaturation and phytotoxicity. Conclusion: This study confirms that properly diluted tofu wastewater can serve as an effective liquid organic fertilizer to improve crop growth and physiological quality, offering a cost-efficient and eco-friendly solution that promotes nutrient recycling, waste valorization, and sustainable agricultural practices within a circular economy framework.