Enhancing Rice Seedling Growth in Acidic Soil Using Fermented Raw Rice Husk as Soil Amendment

Raw rice husk (RRH), rich in cellulose, lignin, silica, has the potential as a soil amendment due to its low bulk density. However, its use in developing countries is limited by the difficulties in transforming it into economically viable items. This study investigated the efficacy of pre-treating RRH with acetic acid, calcium hydroxide, and molasses to enhance its decomposition and promote microbial activity. The research focused on employing Bacillus sp. to create soil amendment from pre-treated RRH, molasses, and cow manure, and evaluates their impact on rice seedling growth and soil quality under various conditions. RRH was pretreated using tap water, acetic acid, calcium hydroxide, and molasses, followed by fermentation with three strains of plant growth-promoting rhizobacteria (PGPR): Bacillus siamensis, Bacillus amyloliquefaciens, and Bacillus velezensis. The resulting fermented RRH was evaluated for its ability to enhance rice seedling growth in pot experiments under normal, acidic, and saline soil conditions. Soil amendments from pretreated RRH enhanced soil remediation created by increasing pH and reducing electric conductivity was effective in delivering beneficial microorganisms, ensuring their survival under stress. Calcium hydroxide pretreatment combined with Bacillus sp. inoculation significantly improved early rice seedling growth (root and shoot length, biomass) in acidic and saline conditions, outperforming chemical fertilizers and reducing plant salt stress. The study found that pre-treating RRH with acetic acid, calcium hydroxide, or molasses is an environmentally acceptable and cost-effective alternative to chemical fertilizers, promoting microbial movement in soil amendments. This approach works especially well in acidic paddy fields, decreasing the requirement for mineral fertilizers.