Compost and vermicompost in cucumber rhizosphere promote plant growth and prevent the entry of anthropogenic organic pollutants

An accurate assessment of the absorption and accumulation of soil pollutants by plants is essential to avoid the entry of toxic compounds into the human and animal food chain. Therefore, this study evaluated the effectiveness of the amendment of a loamy soil with a mixed compost (CP) and a vermicompost (VC) from digestate, at doses of 10 t ha-1 (CPL and VCL) and 30 t ha-1 (CPH and VCH), in sustaining the growth of cucumber (Cucumis sativus L.) plants and reducing the uptake of contaminats, such as the fungicide metalaxyl-M (MET-M) and the endocrine disruptors bisphenol A (BPA), 4-tert-octylphenol (OP) and nonylphenol (NP). Plant response to soil amendment with CP and VC was tested in parallel in both contaminated and uncontaminated soil. All treatments significantly promoted cucumber growth in both soil conditions. After 38 days of cucumber growth in contaminated soil, CPL, CPH, VCL and VCH increased dry biomass of roots and shoots by 42, 128, 118, 147%, and 46, 113, 271, 443%, respectively, compared to unamended soil (control). Root and shoot elongation and the number of leaves and their expansion were also significantly promoted by the application of CP and VC at both doses. All treatments, in the order: VCH > VCL > CPH > CPL, considerably reduced the absorption of all compounds by cucumber. Although small quantities of residues of each pollutant were found both in the roots and in the aerial organs of all plants, their overall accumulation in plants grown in amended soil was significantly lower than that found in the control plants. Thus, on the basis of the results obtained, it is evident that the use of CP and VC can be very effective and sustainable both from an economic and environmental point of view, since, in addition to stimulate plant growth, it can represent a successful strategy to mitigate the presence of toxic residues in food plants.