EFFECT OF BIOCHAR ON SOIL CADMIUM CONTENT AND CADMIUM UPTAKE OF COTTON (GOSSYPIUM HIRSUTUM L.) GROWN IN NORTHWESTERN CHINA.

In order to investigate the effects of biochar on soil cadmium (Cd) content in northwestern China, we used cotton (Gossypium hirsutum L.) straw charcoal in a 2-year experiment involving different doses of both biochars (1.5% (C1) and 3% (C2)) and Cd (1 mg·kg^-1 (H1), 2 mg·kg^-1 (H2), and 4 mg·kg^-1 (H3)) in addition to the treatments, control plots were set up with no biochar application. We grew cotton (Gossypium hirsutum L.) in pots for each treatment and examined soil pH, Cd forms, and Cd accumulations in aboveground plant organs. Compared to no added biochar, the addition of biochar significantly increased soil pH, but there was no notable difference in soil pH between the C1 and C2 treatments. Biochar significantly decreased soil-available Cd with this effect increasing with higher biochar doses. The lowest amounts of soil-available Cd in all Cd treatments (H0–H3), including the control, occurred later in the study, typically at 90 to 150 days post treatment. In the cotton (Gossypium hirsutum L.), Cd preferentially accumulated the most in leaves, then in stems, and then in bolls and the amount of Cd in cotton and soil-available Cd significantly correlated. The addition of biochar promoted the transformation of exchangeable and carbonate-bound Cd to organic matter-bound Cd at 30, 60, and 90 days, and the exchangeable and carbonate-bound Cd to Fe-Mn oxide-bound Cd at 120 and 150 days. In conclusion, biochar addition decreases both Cd bioavailability and the accumulation of Cd in cotton (Gossypium hirsutum L.) aboveground organs. [ABSTRACT FROM AUTHOR]