Soil and plant growth response and trace elements accumulation in sweet corn and snow pea grown under fresh and carbonated coal fly ash amendment

With the recent focus of using coal combustion residue fly ash in mineral carbonation for C capture, an end product, carbonated coal fly ash is generated. The physicochemical changes occur in fly ash during carbonation is hypothesized to improve its soil application potential compared to original fly ash. Therefore, in the present study, we tested carbonated coal fly ash against non-carbonated (fresh) ash for its effect on soil, plant production, and elemental accumulation in plant parts. Plant pots of sweet corn (Zea mays L.) and snow pea (Pisum sativum L.) added with fresh or carbonated Australian coal fly ash to sandy loam Podosol soil at 5% (w/w) and 10% (w/w) mixing rates were used in the study. Alkalinity of fly ashes attenuated the strong acidity of the soil into weakly acidic to slightly alkaline ranges. Either fresh or carbonated fly ashes added trace elements such as B, Fe, Mn, Zn, Cu, Cd, Mo, Cr, Pb, and Ni into the soil which significantly enhanced the plant growth and yield compared to fly ash absent pots. Accumulation of heavy metals in plant parts were observed in fly ash-treated pots. Fresh fly ash at 10% (w/w) application rate increased the soil salinity above admissible range and retarded the crop growth and yield. Carbonated fly ash continued to enhance the crop production of sweet corn and snow pea up to 10% (w/w) mixing rate. Carbonation has improved the fly ash from its original state to make it a safer soil amendment at higher dosages such as 10% (w/w).