Eco-friendly Liquid Fertilizers from Dal Lake Macrophytes: A Dual Assessment of Quality and Bio-efficacy

The unchecked proliferation of aquatic macrophytes has emerged as a critical driver of eutrophication, accelerating ecological degradation and exacerbating the environmental decline of Dal Lake, India. This study investigates a sustainable resource management approach by converting these problematic aquatic macrophytes into value-added fermented liquid fertilizers (FLFs) for agricultural application. Nine distinct FLFs were produced from biomass collected across nine sampling sites in Dal Lake using lactobacilli-driven fermentation. As a preliminary proof-of-concept for macrophyte valorization from the Dal Lake into liquid fertilizers, this study provides a comprehensive characterization of the FLFs' physicochemical properties, nutrient profiles, heavy metal safety, and biostimulant potential. The FLFs exhibited favorable pH and electrical conductivity, along with appreciable levels of essential macro- and micronutrients. Heavy metals such as Cr and Cd were within regulatory limits, with Pb undetected, affirming their safety for agricultural use. The detection of indole-3-acetic acid (IAA) further demonstrates intrinsic biostimulant potential. Seed germination bioassays using Brassica oleracea var. viridis (collard greens) and Raphanus sativus (scarlet globe radish) demonstrated enhanced seedling vigor. Enhanced germination was observed at 1:20 dilution for collard greens (SVI: 105.71−188.16%) and 1:10 dilution for radish (SVI: 156.08−290.98%). Collectively, these findings establish a scalable circular economy framework for nutrient recovery and ecological restoration in eutrophic freshwater systems.