Biochar improves cd-contaminated soil and lowers Cd accumulation in Chinese flowering cabbage (Brassica parachinensis L.)

Biochar is porous and rich in functional groups on its surface. When applied to Cd-contaminated soils, it can reduce Cd availability and decrease Cd uptake by crops. However, the combined effect of biochar application with vegetables on soil biogeochemistry is often neglected. In the pot experiment of this study, biochar (B) derived from straws of Pennisetum hydridum was applied (2% by weight) to a Cd-contaminated soil planted with two cultivars of Chinese flowering cabbage (Brassica parachinensis L.): Bilvcutai (C+B) and Teqingchixin#4 (T+B). The results showed that in C+B and T+B, soil textures were loam, while CK, C, T were silty loam, and B was sandy loam; soil moisture increased by 19 % and 12 %, respectively; soil pH increased significantly by 0.29 and 0.30 units, respectively; soil organic matter increased by 28 % and 11 %, respectively; soil cation exchange capacity increased by 40 % and 29 %, respectively; Urease, neutral phosphatase, and sucrose activities did not change significantly in C+B, but urease activity increased significantly while phosphatase activity decreased sign ificantly in T+B; Bacterial abundance increased 3.7-and 3.4-fold, and fungal abundance increased 1.2-and 1.7 fold, while actinomycete abundance increased 2.4-and 1.6-fold in C+B and T+B, respectively; soil available nitrogen increased by 38 % and 58 %, respectively; soil available phosphorus increased by 55 % and 66 %, respectively; while soil available Cd was decreased by 30 % and 25 %, respectively. In addition, biochar application improved vegetable gowth, and the plant Cd content in the roots decreased by approximately 18 % and 14 % in C+B and T+B, respectively, and that in the aboveground parts decreased by approximately 10 % in C+B and T+B. Thus, biochar application improved soil fertility and quality while reducing Cd bioavailability and uptake by Chinese flowering cabbage.