Rice straw biochar mitigates metal stress in maize and assists in the phytoattenuation of a slag-contaminated soil

Abstract

Abstract Soils polluted by heavy metals soils pose a high risk to human health and must be remediated. Applying biochar to such soils can reduce metal bioavailability and phytotoxicity, improving phytoremediation techniques. This work aimed to assess the effects of rice straw biochar (RSB) on mitigating metal stress and accumulation of Si, Cd, Pb, and Zn in maize plants grown in soil contaminated by metallurgy slag. The soil in pots was amended with RSB rates equivalent to 0.0, 5.0, 10.0, 20.0, and 30.0 t ha-1 and grown with maize for 45 days. Chlorophyll fluorescence, photosynthetic pigment contents, and gas exchange parameters were evaluated as metal toxicity indicators. The RSB rates significantly increased Si uptake while reducing Cd, Pb, and Zn accumulation in maize shoots. The addition of 30.0 t ha-1 RSB promoted 18, 34, and 37% reductions for Zn, Cd, and Pb in the plants. Photosynthetic rate, transpiration, and stomatal conductance increased by 68%, 67%, and 55%, while chlorophyll a, b, and carotenoid contents increased by 77%, 57%, and 42%, correspondingly. Chlorophyll fluorescence measurements showed a linear and positive relationship between photosystem II energy consumption efficiency (Fv/Fm) and RSB rates. Applying RSB associated with maize cultivation can assist in the phytoattenuation of Cd, Pb, and Zn contamination in soils since RSB increases biomass and the plant's tolerance to metal stress.