Combined effects of biochar and chicken manure on maize (Zea mays L.) growth, lead uptake and soil enzyme activities under lead stress.

The goal of the present work was to evaluate the additive effects of biochar and chicken manure on maize growth in Pb-contaminated soils. In this study, we conducted a pot experiment to investigate how biochar in soil (20, 40 g·kg-1), chicken manure in soil (20, 40 g·kg-1), or a combination of biochar and chicken manure in soil (each at 20 g·kg-1) effect maize growth, Pb uptake, leaves' antioxidant enzymatic activities, and soil enzyme activities under artificial conditions to simulate moderate soil pollution (800 Pb mg·kg-1). The results showed that all biochar and/or chicken manure treatments significantly (P < 0.05) increased maize plant height, biomass, and superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activity but decreased the malondialdehyde (MDA) content. These results indicated that amending the soil with biochar and/or chicken manure could alleviate Pb's phytotoxicity. The biochar and/or chicken manure treatments remarkably decreased the Pb concentration in maize roots, stems, leaves, bioconcentration factor (BCF), translocation factor (TF), and available Pb concentration in the soil. Amending the soil with chicken manure alone was more effective at increasing maize growth and antioxidant enzymatic activity; the biochar treatment alone was more effective at inducing soil alkalinization and contributing to Pb immobilization. The combined use of biochar and chicken manure had an additive effect and produced the largest increases in maize growth, leaves' antioxidant enzymatic activity, and soil enzyme activity. Their combined use also led to the most significant decreases in maize tissues Pb and soil available Pb. These results suggest that a combination of biochar and chicken manure was more effective at reducing soil Pb bioavailability and uptake by maize tissues, and increasing maize growth. This combination increased plant height by 43.23% and dry weight by 69.63% compared to the control.