Effect of organic amendments on the alleviation of cadmium in red amaranth (Amaranthus gangeticus) grown in Cd-contaminated saline soils

Cd-contaminated saline soil is now becoming a serious threat affecting sustainable agriculture throughout the world. In this study, organic amendments (OA) were applied to Cd-contaminated saline soils to, firstly, reduce the bioavailability of Cd in soil and, secondly, minimize Cd accumulation in red amaranth (Amaranthus gangeticus) plant. The soil was treated with 1% and 2% of cow dung (CD), vermicompost (VC), waste tea (WT), saw dust (SD), rice hull (RH), and compost. Red amaranth (Amaranthus gangeticus) plant was grown using a pot experiment in control and OA-treated soil stressed with both salinity (4 dsm⁻¹ and 8 dSm⁻¹) and Cd (5 mgkg⁻¹). In slightly saline conditions (4 dSm⁻¹), the addition of 1% CD and VC reduced the bioavailable Cd in the soil to 17.44% and 15.12%, respectively. The reduction increased to 24.42% and 25.58% with 2% rate of application in the same soil. However, in moderately saline soil (8 dSm⁻¹), the reduction varied significantly only with the higher rate. Shoot Cd content was reduced by 85.86% using 2% VC in low saline soil. The bioconcentration factor was also lowered with the addition of CD and VC; however, the performance proved to be better in low saline soil at 2% rate of application. The health risk index (HRI) value for the adults was observed to be < 1 only when the soil with low salinity was treated with 2% VC. Consequently, VC can be used in Cd-contaminated saline soils for red amaranth cultivation to reduce risks to people’s health.