Impact of fly ash application on leaching and concentration of heavy metals and nutrients uptake by maize (Zea mays) on peat soil

<h2>Abstract</h2> Indonesia generates a substantial volume of fly ash (FA) from thermal power plants, necessitating research into its potential utilization. This study evaluated the effects of mixed fly ash (MFA), produced by co-firing 70 % coal and 30 % biomass wood waste on the leaching and uptake of heavy metals and nutrients by maize grown on peat soil. A greenhouse and laboratory experiment were conducted at the Indonesian Soil Research Institute using a randomized block design with eight treatments, including a control and varying MFA doses combined with NPK fertilizer. The hybrid maize variety Bisi-18 served as the indicator plant. Observed parameters included initial soil properties, concentrations of heavy metals and nutrients in leachate and plant tissues, plant height, leaf number, root and shoot biomass, grain yield, and nutrient uptake. Results showed that leachate from the MFA 140 g/pot treatment contained Pb (0.3 mg/kg), Cd (0.01 mg/kg), Co (0.05 mg/kg), and Ni (0.02 mg/kg) all below critical thresholds. The 105 g/pot MFA application significantly enhanced maize growth, nutrient uptake, and grain yield (96.3 g/pot). These findings indicate that MFA poses no negative environmental impact and can improve the productivity of peat soils. Therefore, MFA is environmentally friendly and can be used as a soil amendment on peat soil.