Synergistic Effects of Compost and Biochar on Lead and Cadmium Remediation in Contaminated Soils grown to Amaranthus hybridus

The study investigates the combined use of compost and biochar for soil remediation. It evaluates the effectiveness of biochar from maize cob and poultry litter, in combination with compost, in reducing the availability of lead (Pb) and cadmium (Cd) in contaminated soils. Pot experiment was conducted in a controlled environment using soils from an iron-pot industry dumpsite and a contaminated fadama (valley bottom) soil. Using the rate of 10.7 g/kg, maize cob and poultry litter were combined with compost in ratio 0:0, 1:4, 2:3, 4:1 and 3:2 and applied to soils grown to Amaranthus hybridus, that was laid in randomized complete block design. 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 found that increasing the compost in the combination with biochar improved plant height, leaf area, and biomass yield. The application of 60% poultry litter biochar and 40% compost gave the highest remediation of 68 and 55% remediation for Pb and Cd, respectively, in the iron-pot industry dumpsite soil, and 68 and 42% remediation in the contaminated fadama soil, for the respective metals. The combination ratio 3:2 was also most effective in reducing Pb and Cd concentrations in Amaranthus hybridus. The study also highlights the importance of soil pH in influencing metal mobility and plant uptake. Overall, the findings suggest that combining biochar with compost (3:2) can enhance soil remediation while supporting agricultural productivity.