Influence of biofertilizer on heavy metal bioremediation and enzyme activities in the soil to revealing the potential for sustainable soil restoration

Abstract

Overuse of chemical fertilizer and pesticides in agricultural activity is frequently damaging to soil health and can accumulate heavy metals in the soil environment, causing harm to plants, humans, and the ecosystem. This study was done to evaluate the effectiveness of biofertilizers in reducing heavy metal levels in contaminated soil and enhancing the activity of soil enzymes that are crucial to plant growth and development. Two bacteria strains, Pseudomonas aeruginosa. and Bacillus firmus, were chosen to develop biofertilizers based on molasses. The pot experiment was setup using a completely randomized design with four treatments and five levels; Bacillus firmus and Pseudomonas aeruginosa were used separately, and they were combined for the biofertilizer dose (20, 40, 60, 80, and 100 mL). Utilizing contaminated soils taken from a greenhouse farm the effect of biofertilizer on heavy metal bioremediation and soil enzyme activity was examined. Methods of soil agrochemical analysis were used to determine the soil physiochemical properties and the concentrations of heavy metals Cu, Fe, Zn, Cd, Mo, Mn, were determined by inductively coupled plasma–mass spectrometry ICP-MS, following DTPA extraction methods. In results, soil pH decreased from 8.28 to 7.39, Ec increased from 0.91 to 1.12, organic matter increased from 18.88 to 20.63 g/kg, N increased gradually from 16.7 to 24.4 mg/kg, and K increased from 145.25 to 201.4 mg/kg. The effect of biofertilizer treatment on soil physiochemical characteristics was significantly positive. Application of biofertilizer significantly increased the heavy metal bioavailability and the activities of soil enzymes. Soil pH were positively correlated with soil Zn (0.99819*), APK (0.95869*) activity and negatively correlated with Fe (0.96759*) also statistically significant at (p < 0.05). The soil Cu positively correlated with Fe (0.99645*), Cd (0.97866*), β.D.GLU (0.99769*) and negatively correlated with PAK (− 0.9624*). Soil ARY had positive correlation with soil Mn (0.99683*), Cd (0.95695*), and negative correlation with PAK (− 0.99424*) at (p < 0.05). Soil enzyme activities were negatively correlated to heavy metals at a significant level. Collectively, the study highlights the potential of biofertilizers as a sustainable and effective approach to enhance soil health and remediate heavy metal-contaminated soils in greenhouses.

Combined Application of Biochar and Plant Growth-Promoting Rhizobacteria Improves Heavy Metal and Drought Stress Tolerance in Zea mays

“…Further, in the combined stress condition, the ARN7 + GS-BC treatment improved these enzyme activities by several fold, suggesting that the combined application significantly improved the microbial activity in the rhizosphere soil by improving soil physical, chemical, and biological properties. Similar results have been reported by Haroun et al [ 10 ], Ma et al [ 37 ], and Jabborova et al [ 44 ], where the application of PGPR and biochar improved the activity of soil enzymes under HM and drought stress conditions. Several mechanisms have been explained [ 14 , 45 , 46 ] which correlate the application of BC and/or PGPR with their effect on soil enzymes under adverse environmental condition.…”

“…The improvement in plant growth parameters as the consequence of ARN7 treatment align with prior findings [ 18 , 20 , 27 ], indicating that the PGP metabolites of ARN7, including siderophores, IAA, exopolysaccharides, and phosphate solubilization, contribute to the enhancement of Z. mays growth under HM and drought stress. On the other hand, biochar has also been extensively investigated as a soil amendment to boost plant growth and enhance soil properties [ 10 , 13 ]. It has been shown to enhance nutrient availability, water retention capacity, and soil structure, all of which positively influence plant growth and stress resilience [ 28 ].…”

“…[ 7 , 8 , 9 ]. An increment in the activity of extracellular enzymes including β-glucosidase, which is involved in soil nutrient cycling, has also been reported with the addition of biochar in HM-contaminated soils [ 10 , 11 ]. Similarly, recent studies have also found that biochar amendment is an effective drought mitigation strategy as it improves soil’s water holding capacity and water retention and thus plant water-use efficiency by holding water in the pores and slowly releasing it under drought condition [ 12 , 13 ].…”

Microbiological Mechanisms of Collaborative Remediation of Cadmium-Contaminated Soil with Bacillus cereus and Lawn Plants

“…After planting Festuca arundinacea and Poa pratensis, the soil total nitrogen and available phosphorus contents showed a trend of increasing first and then decreasing with the increase in the bacterial liquid concentration, but they were all higher than those in the control treatment. The application of Bacillus cereus can increase the soil available phosphorus content, possibly due to the enhancement of soil phosphatase activity by Bacillus cereus by promoting the conversion of organic phosphorus to available phosphorus in the soil, which is similar to the findings of Haroun et al [22]. Many studies have reported that soil nutrient content is closely related to plant growth.…”

Evaluation of Acacia karroo’s Potential Aspect in the Phytoremediation of Soil Pollution

“…The concentration levels of Zn, Rb, Sr, and Y showed a significant positive correlation with the activity of CAT and PHO but a negative association with the INV activity. Haroun et al, 2023, reported a similar discovery, where the soil enzyme activities showed a significant negative correlation with heavy metals [41]. Another study by Yang et al, 2022, reported different results in correlation analysis.…”