Aquatic Plant-Based Biostimulants: Comparative Evaluation of Sargassum sp. and Eichhornia crassipes Extracts for Rice Growth Promotion

Abstract

Aquatic weeds are abundant biomass resources, yet their conversion into compost extracts for rice establishment remains insufficiently evaluated across the transition from seed germination to nursery growth. This study examined compost extracts from Sargassum sp. and water hyacinth (Eichhornia crassipes) as stage-specific nutrient-biostimulant inputs for Oryza sativa L. A randomized block design was used for germination, combining four extract types (biohumic, Sargassum sp., water hyacinth, and their mixture) with four concentrations (25, 50, 75, and 100 mL L-1). Extract chemistry and treatment means were interpreted conservatively because ANOVA did not detect significant treatment effects. The results showed Sargassum sp. extract had higher organic C, C/N ratio, K-equivalent concentration, and pH, whereas water hyacinth had higher N. Biohumic at 25 mL L-1 showed the highest germination means for plumule length, radicle length, leaf number, and fresh mass. The results support a cautious, hypothesis-generating model in which extract performance depends on rice developmental stage. Low-dose humic input appears more suitable for germination, whereas higher-dose aquatic weed extracts may be more useful during nursery growth