Enhancing arsenic and cadmium phytoextraction and soil microbial response with fertilizers or oxalic acid in Pteris vittata L. and Sedum alfredii Hance intercropping system

Pteris vittata L. and Sedum alfredii Hance intercropping system has been proved to remediate arsenic (As) and cadmium (Cd) co-contaminated soil. In this study, a greenhouse experiment was conducted to investigate the efficiency of using fertilizers [organic fertilizer (OF), calcium magnesium phosphate (CMPF), and compound fertilizer (CF)] and oxalic acid (OA) to enhance phytoextraction of As and Cd in this intercropping system. The results indicated that these amendments could promote plant growth and enhance As/Cd contents in hyperaccumulators. The total accumulation of As and Cd from OA treatment per pot was enhanced by 91.2 % and 74.3 %, followed by CMPF and CF treatments. The available contents of As and Cd from OA treatment were the lowest with decrease by 16.0 % and 20.6 % in comparison to control treatment, respectively, and enzyme activities were improved. Proteobacteria was the domain phylum accounting for 25.7 %-31.8 %, followed by Chloroflexi (19.7-23.2 %), Actinobacteria (18.8 %-21.9 %), Acidobacteria (8.10 %-10.9 %), and Gemmatimonadetes (5.21 %-6.85 %). The relative abundance of Sphingomonas was positively correlated with As accumulation, and there was a positive relationship between Roseiflexaceae, Gemmatimonadaceae and Cd accumulation. OA and CMPF were suitable amendments for enhancing As and Cd accumulation and alleviating toxicity in the intercropping system of P. vittata with S. alfredii.