EFFECTS OF SINGLE AND COMBINED AMENDMENTS ON CADMIUM AVAILABILITY AND CROP UPTAKE IN THE PURPLE AND BLACK SOILS UNDER CORN -WHEAT ROTATION

Soil cadmium (Cd) pollution endangers the human health through the food chain and has become a serious concern in China. The study was to investigate the effects of amendments on Cd availability and uptake by crop in contaminated soils after calcined lime (C), hydroxyapatite (H) and pig manure (P) were applied alone and combination to the purple and black soils under corn-wheat rotation. Results showed that crop biomass, Cd concentration, soil pH, DTPA extractable Cd and Cd fractions were significantly changed when applying amendments into both soils. Calcined lime and hydroxyapatite could significantly decline Cd availability in both soils regardless of crop type, and application of hydroxyapatite and pig manure increased the crop biomass. More obviously Cd fractions changes were observed in corn growing period, especially applied with calcined lime and hydroxyapatite. Calcined lime increased carbonate -bound (Carb-Cd) Cd fractions resulted from 17.17% to 29.23% and from 17.26% to 35.38%, and hydroxyapatite increased Fe- and Mn oxide -bound (Ox-Cd) Cd fractions from 29.54% to 42.91% and from 19.32% to 36.54% in the purple and black soils. However, the exchangeable (Ex-Cd) and organic matter-bound (Org-Cd) Cd fractions were slightly increased after applying pig manure into both soils. Moreover, combined amendments prepared from alkaline materials and organic fertilizers could decrease grain Cd concentrations and increase crop biomass simultaneously. The immobilization effects of combined amendments were more remarkable in the black soil, such as hydroxyapatite + pig manure (HP) and calcined lime + hydroxyapatite + pig manure (CHP). This research demonstrated that Cd availability in soil and Cd uptake by crop root were the main factors to affect Cd immobilization, while the translocation in crop could hardly influence the Cd immobilization.

Automated summary

Soil Cd pollution is a serious concern in China due to its impact on human health through the food chain. This study investigated the effects of amendments on Cd availability in contaminated soils under corn-wheat rotation, showing that lime and hydroxyapatite can reduce Cd availability, while pig manure can increase certain Cd fractions. Combined amendments can decrease grain Cd concentrations and increase crop biomass, with more significant effects observed in black soil.