Soil microbial community variation in vanadium-enriched farmland surrounding vanadium titanomagnetite tailing in Southwest China

Long-term vanadium titanomagnetite (VTM) mining in Panzhihua, China, leads to severe metal pollution in the adjacent agricultural soil, which causes great environmental and health concerns. In this study, the farmland soils with different plants (Grape, Mango, Tobacco, Corn) were collected near titanium-magnetite tailing in the Panzhihua area to investigate the metals (V, Fe, Mn, Ti) contamination and the related microbial response. The study area had a lateritic red soil type and was irrigated with water from a nearby river. The soils with cultivation showed an increase in the pH and a decrease in electrical conductivity (EC) compared with no-till land soil (control). This study's soils presented an average total V at 233.57 mg/kg, with no significant difference (p > 0.005) in different farmland soils. The planted soil presented more proportion of available Fe and Mn than unplanted soil, but there was no significant difference in the proportion of available V and Ti. Soils with different plants showed varied available metals. Especially the percentage of available V of the total (A-V/V) was highest in the grape planting area, while tobacco planting significantly decreased the availability of V and Ti. Furthermore, the planted soils showed 2.33–3.11 times, 9.50–37.89 times, 0.11–1.20 times, and 5.43–26.46 times higher urease, dehydrogenase, and sucrase activities, and acid phosphatase than the unplanted ones, respectively. The metal resistance genes (van) and integration genes (intl1) were enriched in planted soil. The dominant genera, including Nocardioides and Sphingomonas, were positively correlated with available V, Ti, Mn, and acid phosphatase activity (p < 0.05), which may participate in the enrichment van and intl1. Such knowledge reveals the impact of VTM mining on the agricultural ecological environment and potentially contributes to the risk evaluation of such influenced lands.