Effective alleviation of aluminum phytotoxicity by manure-derived biochar

Abstract

The alleviation of aluminum phytotoxicity to wheat plants in a hydroponic system through the amendment of biochar is investigated to explore the possibility of applying biochar in acidic soil amelioration. Biochar derived from cattle manure pyrolyzed at 400 °C (CM400) and the CM400 biochar washed with distilled-deionized water to remove alkalinity (WCM400) were prepared to determine the roles of the liming effect and adsorption during the alleviation of Al toxicity. Upon addition of 0.02% (W/V) CM400 to the exposure solution, the inhibition of plant growth by Al was significantly reduced while the toxic threshold was extended from 3 to 95 μmol/L Al3+. Due to the biochar liming effect, the aluminum species were converted to Al(OH) 2+ and Al(OH)2+ monomers, which were strongly adsorbed by biochar; furthermore, the highly toxic Al3+ evolved to less toxic Al(OH)3 and Al(OH)4- species. Adsorption of Al by the biochar is dominated by surface complexation of the carboxyl groups with Al(OH)2+/Al(OH)2+ rather than through electrostatic attraction of Al3+ with negatively charged sites. Compared to the liming effect, the adsorption by biochar exhibited a sustainable effect on the alleviation of Al toxicity. Therefore, the biochar amendment appears to be a novel approach for aluminum detoxification in acidic soils. © 2013 American Chemical Society.