The combination of nitrogen fertilizers and EDDS enhances remediation efficiency of Bidens pilosa L. in Cd-contaminated soils

Biodegradable chelating agents and nitrogen (N) fertilizers are widely used for the remediation of heavy metal-contaminated soils due to their ability to promote plant growth, enhance metal mobility and facilitate plant uptake. In this study, a pot experiment was conducted to investigate the effects of nitrate nitrogen (N-NO₃^-), ammonium nitrogen (N-NH₄⁺) and amide nitrogen (N-amide) with different concentrations of 25, 50 and 75 mg N·kg^-1 combined with (S,S)-ethylenediaminedisuccinic acid (EDDS) (1 mmol·L^-1) on growth, biomass and phytoextraction efficiency of Bidens. pilosa L. and the bioavailability of cadmiun (Cd) in 15 mg·kg^-1 Cd-contaminated soil. The results demonstrated that the application of 50 mg N·kg^-1 N-NO₃^- and EDDS not only promoted plant growth and increased biomass, it also changed Cd distribution between operational fractions, increased available Cd content in soil, thereby maximizing the Cd uptake, thus enhancing the Cd enrichment capability of B. pilosa L. This combination achieved the maximum phytoextraction efficiency of 12.12% and the maximum soil Cd removal of 12.38% across all treatments. The comprehensive score obtained using the membership function method also showed that the treatment with 50 mg N·kg^-1 N-NO₃^- and EDDS had the highest score. In conclusion, combination of 50 mg N·kg^-1 N-NO₃^- and EDDS resulted in the greatest biomass production, and highest phytoremediation efficiency, indicating that it has great potential for application in phytoremediation with B. pilosa L. in Cd-contaminated soil.