Natural fermentation of plant tissues as environmental remediation materials to improve soil and enhance plant resistance to cadmium stress

Cadmium (Cd) pollution poses a serious threat to various ecosystems, and phytoremediation is an alternate method for developing the soil health. To better utilize phytoremediation for Cd-contaminated soil remediation, the ginkgo leaves, pine needles, and Eucommia bark were mixed and naturally fermented to obtain Ginkgo biloba–Pinus massoniana–Eucommia ulmoides (GPE) Jiaosu and Jiaosu residue, whose effects on Broussonetia papyrifera planted in Cd-contaminated soil were evaluated. The results showed that the contents of the protein, phenolic, vitamin E, and alcohol of GPE Jiaosu were 4400 ± 0.46, 0.22 ± 0.01, 0.88 ± 0.24, and 4.63 ± 0.25 μL/mL, accordingly, with fine antioxidant activity. The soil pH, electrical conductivity content, organic carbon, total nitrogen, total phosphorus, alkali-hydrolyzable nitrogen, available phosphorus, and Cd concentration were all significantly (p < 0.05) modified. The chlorophyll content of B. papyrifera was increased by using Jiaosu residue in 12 hours, while the promotion effect of Jiaosu appeared in the later stage (60 days). The Cd tolerance physiological indexes such as malondialdehyde content and antioxidant enzymes' activity were all regulated. Applying the Jiaosu residue, the Cd in stems was decreased by 72.61% under 1000 mg/kg Cd treatment. These results suggested that GPE Jiaosu and Jiaosu residue can improve the properties of Cd-contaminated soil, promote the Cd tolerance of B. papyrifera, and affect the Cd migration. The current study provides a new bioremediation method using the Jiaosu and Jiaosu residue as Cd environmental remediation materials in a recyclable pathway, which is a circular and healthy development concept that integrates economic, ecological, and social significance.