The potential of water hyacinth vermicompost as a sustainable alternative to nitrogen, phosphorous, and potassium fertilizer

Abstract

Excessive use of chemical fertilizers results in irreversible soil quality loss, food safety issues, and eutrophication concerns in aquatic ecosystems that promote the growth and spread of invasive weeds such as water hyacinth (Pontederia crassipes (Mart.) Solms) (Pontederiaceae). However, less attention has been given to mitigating wetland pollution and the direct biomass disposal of water hyacinth towards biomass vermicomposting for weed control and sustainable agriculture through integrated fertilizer management. An open-field lettuce (Lactuca sativa L.) growth experiment was conducted to enhance soil quality, promote growth, and manage aphid pests by substituting water hyacinth vermicompost (VC) for nitrogen, phosphorus, and potassium (NPS) (19N-38P₂O₅-7S) fertilizer. A completely randomized block design (RCBD) with three replications was employed, utilizing the recommended NPS fertilizer dose (F1), 2.5 t ha⁻¹ VC (F2), 5 t ha⁻¹ VC (F3), 2.5 t ha⁻¹ VC + 50% NPS (F4), 5 t ha⁻¹ VC + 50% NPS (F5), and unfertilized soil (F6, control). Maximum fresh weight (215–227%), vitamin C (82.1–94.8%), reduced nitrate content (21.1–23.3%), the highest marginal rate of return (157%), the lowest aphid population (52.8–86.6%), and leaf damage (52.9–92.3%) were observed in plants treated with F4 relative to F6. Moreover, F4 and F5 improved the soil quality characteristics (pH, electrical conductivity, total nitrogen, total available phosphorus, total potassium, total organic carbon, and carbon-to-nitrogen ratio) compared to F6. Based on the findings of this study, the use of F4 in similar agro-ecological zones for improved soil quality, pest control, and enhanced lettuce development is recommended. This work demonstrates how VC can be used sustainably to replace the widespread use of chemical fertilizers to enhance soil fertility, promote lettuce growth, reduce pests, and address wetland eutrophication challenges.