Steel Slag as a Sustainable Amendment: Impacts on Rice Yield, Nutrients and Environmental Safety

Background and objective: In South Korea, significant volumes of steel slag are generated annually, often resulting in disposal as solid waste. Concerns persist regarding alkaline leachate from dumping sites migrating into ecosystems and affecting adjacent rice crops. This study evaluated the feasibility of repurposing steel slag as a sustainable soil amendment to improve rice yield and soil health while ensuring environmental safety.Methods: Steel slag was applied at different rates (0, 2, 4, and 8 tons per hectare) to paddy soils during pot experiment, to monitor changes in pH, nutrient availability and crop performance. Pot water pH was analyzed throughout the cropping season. Rice plants were characterized for their grain and straw yield. Plants and soil were also analyzed for heavy metals and plant available nutrients.Results: The results indicate that steel slag significantly increases soil pH from 6.6 to 7.5, neutralizing soil acidity, creating a more favorable environment for rice cultivation. Furthermore, slag application enhanced the availability of essential nutrients including calcium, magnesium, and iron. Notably, plant available SiO<sub>2</sub> increased significantly in correlation with application rates. While vegetative growth parameters such as plant height and tiller numbers remained stable, reproductive yield showed improvement, with ripened grain weight peaking at 29.95 g at 8 ton ha<sup>-1</sup>. Crucially, heavy metals (Cr, Cd, Pb, As) remained undetectable in both the soil and rice components (grain and straw) across all treatments, alleviating immediate toxicity concerns.Conclusion: Steel slag functions as an effective, ecofriendly soil amendment in paddy rice systems. By optimizing soil pH and significantly boosting SiO<sub>2</sub> availability, slag application creates a suitable environment for crop development. The significant increase in grain yield, coupled with the absence of heavy metal accumulation, suggests that steel slag can be successfully transitioned from an industrial byproduct into a valuable agricultural resource, supporting productivity and environmental sustainability.