Cadmium contamination in agricultural soils of Bangladesh and management by application of organic amendments: evaluation of field assessment and pot experiments

In recent years, cadmium (Cd) contamination in agricultural soils and its subsequent transfer to crops is one of the high-priority environmental and public health issues of global concern, especially in densely populated developing countries like Bangladesh. However, no effective strategy has been introduced or implemented yet to manage Cd-contaminated soils in order to sustain agricultural production with no human health risks. In this study, agricultural soil samples were collected from 60 locations of 10 upazilas from Tangail district to assess the extent of soil Cd contamination. The Cd concentration ranged from 0.83 to 4.08 mg kg −1 with a mean of 2.17 mg kg −1 in topsoil (0–15 cm), and from 0.67 to 3.74 mg kg −1 with a mean of 2.10 mg kg −1 in subsoil (16–30 cm). The values of contamination factor (CF) indicated that all the sampling locations were found to be highly contaminated with Cd. Pot trials with the application of different doses of biochar and vermicompost in Cd-contaminated soil (0.8 mg kg −1 Cd) revealed that integrated application of biochar (5 t ha −1 ) and vermicompost (5 t ha −1 ) was the best treatment that significantly ( p < 0.05) reduced plant Cd concentration (72%) and increased the biomass of experimental crop, Red amaranth ( Amaranthus cruentus ). This combined treatment also significantly reduced the uptake of Cr (37%) when co-contamination was present. The study suggests the application of biochar (5 t ha −1 ) in combination with vermicompost (5 t ha −1 ) to reduce human health risk and increase crop production when the soil is loamy sand in texture. Graphical abstract