Combined Use of TiO2 Nanoparticles and Biochar Produced from Moss (Leucobryum glaucum (Hedw.) Ångstr.) Biomass for Chinese Spinach (Amaranthus dubius L.) Cultivation under Saline Stress

Salinity-induced soil degradation poses a significant challenge to agricultural productivity and requires innovative crop-management strategies. In this study, the synergistic effect of biochar and TiO2 nanoparticles (NPs) obtained from moss (Leucobryum glaucum (Hedw.) Ångstr.) biomass on the growth, yield, biochemical, and enzymatic response of Chinese spinach (Amaranthus dubius L.) grown under salinity stress was investigated. Purposely, A. dubius was grown under different combinations of arable soil, biochar, TiO2 NPs, and saline soils. The produced biochar and TiO2 NPs were characterized using microscopy image analysis, X-ray diffraction patterns (XRD), energy-dispersive X-ray spectroscopy (EDX), zeta potential, particle size distribution, and Fourier-transform infrared spectroscopy (FTIR). The results showed that saline stress caused a significant (p < 0.05) decline in growth, yield, and biochemical constituents of A. dubius compared to control treatments. However, the combined application of biochar and TiO2 NPs significantly (p < 0.05) alleviated the saline stress and resulted in optimum fresh weight (30.81 g/plant), dry weight (4.90 g/plant), shoot and root length (28.64 and 12.54 cm), lead number (17.50), leaf area (12.50 cm2/plant), chlorophyll (2.36 mg/g), carotenoids (2.85 mg/g), and relative water content (82.10%). Biochar and TiO2-NP application helped to reduce the levels of stress enzymes such as catalase (2.93 µmol/min/mg P), superoxide dismutase (SOD: 2.47 EU/g P), peroxidase (POD: 40.03 EU/min/g P), and ascorbate peroxidase (3.10 mM/mg P) in saline soil. The findings of this study suggest that the combination of nanotechnology and biochar derived from unconventional biomass can be a viable option to mitigate salinity-related challenges and enhance crop yield.