Enhancement of soil microbial activity and Basil growth by graphene oxide nanoparticles: insights from a growth chamber experiment

The extensive application of graphene oxide nanoparticles (GONPs) across various fields, owing to their unique physicochemical properties, has led to their increasing release into soil ecosystems, raising concerns about potential interactions with soil microorganisms and plants. This study investigated the effects of different GONPs concentrations—0 (control), 200, 300, and 600 mg kg−1 soil—on soil microbial indices after 30, 60, and 90 days of exposure, as well as on the growth performance of basil (Ocimum basilicum L.) under controlled growth chamber conditions (temperature: 25 ± 2 °C; photoperiod: 16/8 h light/dark; relative humidity: 60 ± 5%). Increasing GONPs concentrations and longer incubation periods significantly enhanced all microbial parameters (p < 0.01). At 600 mg kg−1 after 90 days of incubation, basal respiration (BR) and substrate-induced respiration (SIR) increased by 3.3- and 2.2-fold, respectively, while the microbial population rose 48-fold, microbial biomass carbon (MBC) increased by 60%, and dehydrogenase activity (DHA) exhibited nearly a sevenfold enhancement compared to the GONPs-free soil. Likewise, basil growth was markedly promoted, with shoot and root dry weights increasing by 2.8- and 7.9-fold, respectively, and root volume by 4.5-fold. The root-to-shoot ratio, leaf area, and plant height increased by 88%, 78% and 39%, respectively. Chlorophyll a, b, and carotenoid contents also rose by 69%, 96% and 3.1-fold. Overall, GONPs application—particularly at 600 mg kg−1—significantly enhanced soil biological activity and basil productivity, highlighting their potential as a nanomaterial for improving soil health, boosting plant growth, and promoting sustainable agriculture.