The application of biochar and oyster shell reduced cadmium uptake by crops and modified soil fertility and enzyme activities in contaminated soil

Abstract

Soil pollution with cadmium (Cd) has been threatening the human health. In this study, we investigated the possibility of applying biochar and oyster shell to reduce Cd uptake by crops and modify soil quality. A field study based on the rice–oilseed rape rotation was done, and the treatments were comprised without amendments (PA0) and with 15 000 kg ha−1 biochar (PA1), 15 000 kg ha−1 oyster shell (PA2), and 7500 kg ha−1 biochar and 7500 kg ha−1 oyster shell (PA3). Results revealed that both oyster shell and biochar reduced the HOAc-extractable Cd in soil. Compared to PA0, the HOAc-extractable Cd in the PA1, PA2, and PA3 treatments was reduced by 4.76 %–20.79 %, 17.86 %–38.61 %, and 5.95 %–10.89 %, respectively. The cooperative application of biochar and oyster shell reduced the Cd accumulation in brown rice and oilseed by 29.67 % and 19.74 %, respectively, compared to control and thus decreased the hazard quotient (HQ) from the consumption of brown rice and oilseed. The addition of biochar slightly increased soil organic matter. In addition, the available P in the PA2 and PA3 treatments was significantly (p<0.05) increased by 200.96 %–295.92 % and 187.46 %–280.04 % compared to the control. Moreover, the cooperative application of biochar and oyster shell enhanced the activities of urease, catalase, and β-galactosidase by 139.44 %–147.56 %, 10.71 %–34.31 %, and 82.08 %–244.38 %, respectively. These results demonstrated that the utilization of biochar and oyster shell might be an effective pathway to reducing Cd uptake by crops and improving soil fertility and enzyme activities.