Bacterial consortium for improved maize production under oily sludge

Abstract

AbstractOily sludge contains a wide range of carcinogenic and toxic organic and inorganic compounds that enter into the terrestrial environment and may be toxic to plants. Plants grown over oily sludge–contaminated soil may undergo changes in physiology and in the antioxidant enzymes system due to the presence of toxic hydrocarbons. Information is scarce regarding the inoculation of oily sludge on the changes in the physiology of plants. The present study evaluated the effect of a constructed bacterial consortium and fertilizers on maize (Zea mays L.) growth and survival and on its antioxidant system under the stress environment of 30% and 60% oily sludge. Maize grown over 30% and 60% oily sludge was inoculated with a consortium of plant growth–promoting rhizobacteria strains (Bacillus cereus [Acc KF859972], Bacillus altitudinis [Acc KF859970], comamonadaceae (Delftia) [Acc KF859971], and Stenotrophomonas maltophilia [Acc KF859973]). The bioavailability of some phytotoxic trace elements was also evaluated. Germination was inhibited when plants were grown without inoculation; however, no inhibition to the germination of maize was observed when bacterial consortium was added to oily sludge. A significant difference in the bioavailability of Cu and Zn was observed under maize rhizosphere oily sludge inoculated with consortium. Germination rate, protein, superoxide dismutase, and peroxidase in bacterial consortium–inoculated maize was higher in plants grown in oily sludge compared with plants grown in untreated sludge. The bacterial consortium suppressed the oxidative stress of plants grown in oily sludge and enhanced maize tolerance to oily sludge. The bacterial consortium can be used for enhancing plant nutrient uptake and to increase biochemical and plant enzymes and can be used by oil refineries to remediate soils contaminated with oily sludge.