Synergistic bioaugmentation and biostimulation enhance peanut (Arachis hypogaea) productivity in diesel- and waste-oil-contaminated soils

Abstract

This study aimed to improve the productivity of peanut (Arachis hypogaea) cultivated in soils polluted with diesel and engine oils, a type of contamination known to disrupt soil structure, reduce fertility, and limit crop yields. To address this challenge, indigenous microflora were isolated from a previously contaminated experimental plot and used to develop biodegradation treatments capable of enhancing both pollutant removal and plant performance. The experimental approach involved applying individual and combined strategies of bioaugmentation, using Rhodococcus erythropolis or an indigenous bacterial consortium, and biostimulation, using poultry manure or Bacillus amyloliquefaciens. Pollutant degradation, along with peanut growth, physiological responses, and yield attributes, was systematically monitored. The results identified a competent indigenous microflora composed of strains affiliated with Micrococcus, Lactobacillus, Planococcus, Achromobacter, and Serratia. Combined treatments produced the most substantial benefits, significantly improving plant vigor and yield while accelerating petroleum hydrocarbon removal. The highest degradation rates were achieved with Consortium + poultry manure (76.2%), R. erythropolis + poultry manure (76.9%), Consortium + B. amyloliquefaciens (84.38%), and R. erythropolis + B. amyloliquefaciens (98.57%). These synergistic combinations consistently outperformed single-factor treatments. The findings demonstrate that integrating bioaugmentation and biostimulation is an effective approach for restoring the health and fertility of petroleum-polluted soils. Such combined strategies not only enhance the biodegradation of diesel and engine oils but also substantially improve peanut growth and productivity, offering a sustainable and applicable solution for managing contaminated agricultural lands.