Preliminary Evaluation of Physicochemical Properties and Pre-emergence Efficacy of Fermented Coconut Water-Based Natural Herbicide Against Asystasia gangetica
Abstract
The intensive and persistent use of synthetic herbicides has triggered ecological crises and induced resistance in invasive weeds, such as Asystasia gangetica. Exploring environmentally friendly control alternatives utilizing organic waste, such as the bioconversion of fermented coconut water and garlic, is highly necessary. This study aims to evaluate the physicochemical dynamics of coconut water fermentation and to test the preliminary efficacy of this natural herbicide formulation against the seed viability of A. gangetica in soil media in a greenhouse. The formulation was fermented anaerobically for 14 days, with physicochemical observation intervals every two days. The pre-emergence efficacy test was structured using a single-factor Randomized Complete Block Design (RCBD) with five concentration levels (0%, 5%, 10%, 15%, and 20%) and five replications. Physicochemical results indicated an exponential decrease in acidity, reaching an extreme pH (3.02), and a surge in dissolved solids (2740 ppm) by day 14. Despite the formulation's high acidity, the Analysis of Variance (ANOVA) confirmed that all concentration levels had no significant effect on germination rate, germination capacity (89.80–93.40%), morphological growth, and seedling dry weight biomass. This ineffectiveness is attributed to rapid acid neutralization caused by the pH buffering capacity of Ultisol, the biodegradation of organosulfur agents in the soil ecosystem, and the impermeability of the A. gangetica seed testa. Based on these preliminary findings, fermented coconut water-based natural herbicide is not recommended for pre-emergence weed control applications in the soil but should be exclusively developed for post-emergence foliar contact applications.
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