Comparative Study of Compost and Biochar Application Rates for Lead and Cadmium Remediation in Contaminated Soils grown to Amaranthus hybridus

This study evaluates the effectiveness of biochar, derived from maize cobs and poultry litter, and compost in remediating soils contaminated with lead (Pb) and cadmium (Cd) using Amaranthus hybridus as a test crop. Pot experiment was conducted using soils from an iron-pot industry dumpsite and a contaminated fadama (valley bottom) soil, treated with varying application rates of biochar (maize cobs and poultry litter) and compost (0, 5, 10, and 15 g/kg). Growth parameters, Biomass Yield, Remediation percentage, lead and cadmium in the soils and plant were determined 6 weeks after planting, following standard procedures. Data were analyzed using descriptive statistics, polynomial regression and ANOVA at α0.05, It was observed that increasing the application rate of both amendments significantly enhanced the remediation efficiency of Pb and Cd in both soil types, reducing their availability and accumulation in Amaranthus hybridus. The highest remediation was observed at 15 g/kg poultry litter biochar, which achieved 55% and 48% remediation for Pb and Cd, respectively, in the iron-pot industry dumpsite soil, and 56 and 47% remediation in the contaminated fadama soil, for the respective metals. Similarly, this treatment reduced heavy metal uptake by Amaranthus hybridus, enhancing soil pH and reducing metal mobility. The optimal application rate for effective remediation was determined to be between 8.2 and 10.7 g/kg. These findings suggest that biochar, particularly from poultry litter, is effective for mitigating heavy metal contamination in the contaminated soils.