Remediation of cadmium contaminated soil by composite spent mushroom substrate organic amendment under high nitrogen level.

Cadmium (Cd) contamination in soil poses a serious threat to ecological environment and crop quality, especially under high nitrogen level. Here, the efficiency of composite organic amendment (spent mushroom substrate and its biochar) on remediation of Cd contaminated soil under high nitrogen level has been studied through a 42 days' soil incubation experiment. The results showed: (i) the application of composite organic amendment minimized the repercussions of high nitrogen and significantly reduced the exchangeable Cd proportion by 28.3%-29.5%, especially for Ca(NO) treatment; (ii) the application of composite organic amendment improved the physicochemical properties of soil, such as pH, CEC and organic matter content increased by 0.63-0.99 unit, 39.69%-45.00% and 7.77%-11.47%, and EC decreased by 16.21%-44.47% compared with non-amendment Cd-contaminated soil, respectively; (iii) the application of composite organic amendment significantly increased the soil enzyme activities and microbial biomass, among which urease activity was increased most by 12.06-16.42 mg·g·d, and the copy number of AOA was decreased by 30.6%- 92.0%, and the copy number of AOB was increased most by about 45 times. In brief, the composite organic amendment can alleviate the adverse effects of Cd and nitrogen on the soil, but its long-term efficacy needs to be verified in further field study.