Microbial phytoremediation of chromium-contaminated soil with biogas slurry for enhancing the performance of Vigna radiata L.

Abstract

Chromium (Cr) is a toxic heavy metal and severely reduces plant growth. It commonly exists in two forms, i.e., Cr+3 and Cr+6. Due to the high solubility and oxidizing potential, Cr+6 is more dangerous and can be converted into a less toxic form of Cr+3 by different physicochemical and biological techniques. Nitrogen-fixing rhizobia promote the growth of leguminous plants through various direct and indirect mechanisms, and their efficiency can be enhanced by integrating them with various organic amendments. Biogas slurry (BGS) improves the physical properties of soil and serves as an organic source of nutrients for plants and microbes. Rhizobia can convert the metal into a less toxic state, whereas BGS can bind it and make it unavailable for plants. Therefore, the current experiment evaluated the effect of rhizobia and BGS on the growth and yield of mung bean in Cr-contaminated soil. It was observed that individual and combined application of rhizobia and BGS ameliorated the Cr-induced adverse effects on crop growth and yield attributes. Combined application yielded more significant results than their sole application and control under Cr stress. Moreover, a significant decline in Cr uptake by the plant was observed due to the integrated application of rhizobia and BGS compared to the control. The collaborative effect of plant growth-promoting rhizobacteria (PGPR) and BGS can be suitable for improving mung bean growth under Cr-contaminated sites.