Fermented Rice Water: A Source of Plant Growth-Promoting Microorganisms

Abstract

The increasing demand for sustainable agricultural practices has intensified research on eco-friendly biofertilizers derived from natural resources. Fermented rice water (FRW), a common household by-product generated during rice washing, is rich in soluble nutrients and indigenous microbial populations. The present study investigates fermented rice water as a potential source of plant growth- promoting microorganisms (PGPM) and evaluates its effect on the growth of Coriandrum sativum L. Washed rice water was allowed to undergo natural fermentation for three days under ambient laboratory conditions. A significant reduction in pH from 7.5 to 5.0 indicated active microbial metabolism. Fourteen morphologically distinct isolates were obtained using selective and non-selective media. The isolates were screened for plant growth-promoting traits including phosphate solubilization, cellulase activity, and indole-3-acetic acid (IAA) production. Among them, isolates I1, I8, I11, and I12 exhibited comparatively higher IAA production and were selected for consortium development after compatibility testing. Pot trials conducted under sterile and non-sterile soil conditions demonstrated enhanced germination rate, root length, and shoot length in treated plants compared to control. In non-sterile soil, seed soaking treatment showed maximum root elongation (5.3 cm), while microbial consortium application was more effective under sterile soil (3.5 cm). The findings suggest that fermented rice water serves as an inexpensive and sustainable reservoir of beneficial microorganisms with significant potential as a biofertilizer in sustainable agriculture.