Enhancing Sesbania sesban L. (Merr.) growth and metal resilience by synergistic application of Trichoderma harzianum loaded biochar and biochar-zinc oxide nanocomposite

Abstract

Heavy metals in agricultural soil are hazardous to the environment and human beings. So, the current study was hypothesized that Trichoderma harzianum maize biochar (MBT), and maize biochar zinc oxide nanocomposite (MB-ZnO) could effectively stabilize Cd and Cu in a polluted soil and evaluate their synergistic effects on Sesbania sesban L. (Merr.) growth. The biochar zinc oxide nanocomposite and T. harzianum loaded biochar were systematically characterized before applications. In this study, both types of engineered biochar (MB-ZnO nanocomposite and MBT) were applied to influence the growth of S. sesban. These plants were sprayed with various doses (0, 50, 75, 100 mg/L) of MB-ZnO nanocomposite and 2.0% (w/w) MBT. Foliar application of 100 mg/L MB-ZnO nanocomposite clearly reduced Cd and Cu content in the shoots of S. sesban by 30% and 31%, respectively. The combined application of MB-ZnO increased SOD (33.33%), and POD (37.5%) at the concentration of 100 mg /L. Co-applied application of MB-ZnO nanocomposite and MBT diminished Cd and Cu content by 39% and 38%, respectively, and increased soil pH (8.03 to 8.23). Conclusive findings of this study established that the application of the engineered biochar (MB-ZnO nanocomposite and MBT) is an environment-friendly and efficient way to immobilize toxic metals from the soil and improve the physiological, biochemical, anatomical, and antioxidant enzyme activities of the S. sesban plant.

Keywords: MB-ZnO nanocomposite; Metal immobilization; Plant growth; Sustainable agriculture; Trichoderma loaded biochar.

Fig. 1

SEM micrograph of pristine biochar (A) and MB-ZnO (B)

Fig. 2

EDX spectrum (A) and elemental study (B) of MB-ZnO nanocomposite

Fig. 3

XRD spectra of MB-ZnO

Fig. 4

FTIR spectra of MB-ZnO

Fig. 5

TGA graph of the biochar (A) and the nanocomposite (MB-ZnO) (B)

Fig. 6

UV study of MB (A), ZnO alone and MB-ZnO nanocomposite (B)

Fig. 7

SEM micrograph of pure biochar (A), T. harzianum (B), and T. harzianum loaded biochar (C)

Fig. 8

Effects of MB-ZnO on root and shoot of S. sesban in Cd-Cu stressed soil; C (Control), T1 (0 mg/L), T2 (50 mg/L), T3 (75 mg/L), T4 (100 mg/L). Each treatment was performed in triplicate (n = 3). Significant differences were observed at (p < 0.05) using the Tukey test; different letters on the bars indicate the means of three replicates

Fig. 9

Effects of MB-ZnO on fresh and dry weight of S. sesban in Cd-Cu stressed soil. C, T1, T2, T3 and T4. Significant differences were observed at (p < 0.05) using the Tukey test; different letters on the bars indicate the means of three replicates

Fig. 10

Effects of MB-ZnO on Chlorophyll a, Chlorophyll b, and Carotenoids contents of S. sesban in Cd-Cu stressed soil. C, T1, T2, T3, T4 (n = 3). Significant differences were observed at (p < 0.05) using the Tukey test; different letters on the bars indicate the means of three replicates

Fig. 11

Effects of MB-ZnO on RWC, and REL of S. sesban in Cd-Cu stressed soil. C, T1, T2, T3, T4 (n = 3). Significant differences were observed at (p < 0.05) using the Tukey test; different letters on the bars indicate the means of three replicates

Fig. 12

Effects of MB-ZnO on MDA, and H₂O₂ of S. sesban in Cd-Cu stressed soil. C (Control), T1 (0 mg/L), T2 (50 mg/L), T3 (75 mg/L), T4 (100 mg/L). The treatments were performed in triplicates (n = 3). Significant differences were observed at (p < 0.05) using the Tukey test; different letters on the bars indicate the means of three replicates

Fig. 13

Effects of MB-ZnO on sugar, proline, and protein of S. sesban in Cd-Cu stressed soil. C (Control), T1 (0 mg/L), T2 (50 mg/L), T3 (75 mg/L), (100 mg/L) (n = 3). Significant differences were observed at (p < 0.05) using the Tukey test; different letters on the bars indicate the means of three replicates

Fig. 14

Effects of MB-ZnO on Cu level (A) in shoots and roots of S. sesban and Cu (B) in Cd-Cu stressed soil. C, T1, T2, T3, and T4 (n = 3). Significant differences were observed at (p < 0.05) using the Tukey test; different letters on the bars indicate the means of three replicates

Fig. 15

Effects of MB-ZnO on POD, SOD, and CAT of S. sesban in Cd-Cu stressed soil. C (Control), T1 (0 mg/L), T2 (50 mg/L), T3 (75 mg/L), (100 mg/L).Significant variations were examined at (p < 0.05) using the Tukey test; different letters on the bars indicate the means of three replicates (n = 3). Tukey’s test is typically used for comparisons to identify differences between group means after an analysis of variance