Physicochemical Characterization of Agricultural Biomass Fly Ash and Its Effects on Soil Properties and Trace Element Availability in an Acidic Soil

Agricultural biomass fly ash (BFA) has attracted increasing interest as a liming material and nutrient source for acidic soils, although its effects on trace element availability and plant accumulation remain insufficiently understood. This study characterized agricultural BFA and evaluated its short-term effects on soil chemical properties, nutrient and trace element availability, and trace element concentrations in maize biomass. Unlike previous studies focusing primarily on biomass ash characterization or crop performance, this study integrates biomass fly ash characterization with post-harvest soil properties, nutrient and trace element availability, and trace element accumulation in maize biomass. A 60-day greenhouse pot experiment was conducted in an acidic loamy sand using BFA and commercial agricultural lime (CAL) applied at rates corresponding to 0.5×, 1.0×, and 1.5× soil hydrolytic acidity. Both amendments increased soil pH, reduced hydrolytic acidity, and increased base saturation, although CAL produced a stronger liming effect. BFA supplied substantially more K and Mg and increased soil total carbon and electrical conductivity, while CAL was more effective in increasing Ca availability. Changes in soil trace element availability were generally limited, although Zn and Cr increased after BFA application. Trace element responses in maize biomass were element-specific: concentrations of Fe, Cu, Co, and Cd increased, Mn decreased, and Zn and Ni showed no consistent dose-dependent pattern. Nevertheless, the concentrations measured in maize remained within ranges commonly reported for plants grown on uncontaminated soils. PCA supported the contrasting effects of the amendments, associating BFA more strongly with nutrient availability, total carbon, and electrical conductivity and CAL with soil deacidification and Ca enrichment. Under the conditions of this short-term pot experiment, agricultural BFA improved selected chemical properties of acidic soil without causing pronounced increases in trace element accumulation in maize biomass. Field-scale and long-term studies, including chromium speciation, are required before broader agricultural application can be recommended.