Efficiency of biogas slurry and Burkholderia phytofirmans PsJN to improve growth, physiology, and antioxidant activity of Brassica napus L. in chromium-contaminated soil.

Contamination of soil is a major problem globally with colligated danger for ecosystem and human health. Chromium (Cr) is a toxic heavy metal and caused harmful effect on growth and development of plants. Phytostabilization reduced the mobility of heavy metals with addition of amendments which can significantly decrease metal solubility in soil. Phytostabilization can be achieved by application of biogas slurry (BGS) and endophytic bacteria as amendments in the contaminated soils. The present study revealed that the Burkholderia phytofirmans PsJN and BGS improved the growth, physiology, and antioxidant activity and reduced Cr uptake under a pot experiment spiked with Cr (20 mg kg-1 soil). The experiment was designed under completely randomized design, four treatments with three replications in normal and Cr-contaminated soil. The inoculation of endophytic bacteria improved the growth and physiology of Brassica. This study showed that the inoculation of endophytic bacteria stabilized the Cr levels in soil and minimized the uptake by the plant shoots and roots in BGS-amended soil. Similarly, activity of antioxidants such as catalase (CAT), reduced glutathione (GSH), glutathione peroxidase (GSH-Px), and glutathione s-transferase (GST) was decreased to normal with combined treatment of BGS and endophytic bacteria in Cr-stressed soil. Overall, the best results were analyzed by combined treatment of BGS and endophytic bacteria to improve growth, physiology, and antioxidant activity of Brassica and immobilize Cr in soil. Moreover, results emphasized the need to use BGS alone or in combination with endophytic bacteria to optimize crop performance, stabilize Cr concentration, and improve environmental efficiency.