Cow manure and cow manure-derived biochar application as a soil amendment for reducing cadmium availability and accumulation by Brassica chinensis L. in acidic red soil

Organic amendment is a promising, in situ phytostabilization approach to alleviate the phytotoxic effects of heavy metal contaminated soils. The aim of this study was to evaluate the feasibility of cow manure (CM) and its derived biochar (CMB) as a soil amendment on cadmium (Cd) availability and accumulation in low and high Cd-accumulating cultivars of Brassica chinensis L. grown in an acidic red soil. CM and CMB were applied to Cd-contaminated acidic red soil at the rates of 0, 3.0 and 6.0% (w/w). Application of CMB was significantly more effective than that of CM, as it reduced the availability of Cd in soil by 34.3-69.9% and its bioaccumulation in the low Cd accumulator, Aijiaoheiye 333, by 51.2 and 67.4%, respectively. The addition of CMB significantly increased the extractability and accumulation of trace metals (Zn, Mn, Fe, and Cu) by plants and improved plant biomass production. CMB application, combined with utilizing low Cd accumulating cultivars represents a new, sustainable strategy to alleviate the toxic effects on Cd and improve food safety.