Encapsulated Phosphorus-Enriched Biochar Improves Rice Productivity in Alluvial Soil

This study evaluated the effects of phosphorus-enriched encapsulated rice husk biochar on morphophysiological characteristics and yield of rice (Oryza sativa L.) in acidic alluvial soil.The experiment was conducted from May to September 2025 using a completely randomized design with six treatments: control (b0), conventional biochar at 10 tons ha (b1), biochar enriched with 25% phosphorus (b2), biochar enriched with 50% phosphorus (b3), encapsulated biochar with 25% phosphorus (b4), and encapsulated biochar with 50% phosphorus (b5).Each treatment was replicated four times.The novelty of this research lies in integrating sodium alginate-calcium chloride encapsulation technology with phosphorusenriched rice husk biochar to achieve synchronized controlled-release tailored to rice nutrient demand throughout the growth cycle, addressing the specific challenges of phosphorus fixation in acidic alluvial soils.Results demonstrated that phosphorus-enriched encapsulated biochar significantly improved soil chemical properties.The b5 treatment increased soil pH from 4.41 to 5.22 and available phosphorus from 15.49 ppm to 580.91 ppm.Plant growth parameters showed substantial improvements, with b5 producing the highest plant height (134.5 cm), tiller number (34.1), leaf number (156.0), and dry weight (62.3 g) at seven weeks after planting.Yield components were significantly enhanced, with b5 achieving the highest panicle length (28.58 cm), productive tillers (30.13), filled grains per panicle (213.58),100-grain weight (3.11 g), and grain yield per hill (92.58 g), representing a 25.0% increase compared to the control.The encapsulation technology demonstrated superior controlled-release characteristics, maintaining higher soil phosphorus availability throughout the growing season.These findings provide a sustainable and cost-effective strategy to enhance rice productivity on marginal acidic soils while reducing phosphorus fertilizer requirements by up to 30%, thereby contributing to both food security and environmental sustainability through reduced phosphorus losses and eutrophication risks in tropical agricultural systems.The technology's potential for on-farm production using locally available materials facilitates scalability and adoption among smallholder farmers.