Growth, biomass accumulation, essential oil yield, and resource-use responses of sweet basil (Ocimum basilicum L.) to foliar nano-graphene oxide under organic and mineral fertilization

Sweet basil ( Ocimum basilicum L. ) is an important medicinal and aromatic plant, and its biomass production and essential oil (EO) yield are strongly shaped by nutrient management practices. In this two-year open-field study (2022–2023), we examined the response of sweet basil var. ‘Dino’ to foliar nano-graphene oxide (nGO) under organic and conventional fertilization. Farmyard manure (F; 30 t ha –1 ) and NPK fertilization (Ch; 90:60:60 kg ha –1 ) were each combined with foliar nGO at 100, 200, 300, and 500 mg l –1 . Plant growth, biomass accumulation, EO yield, energy use efficiency, and economic performance were then evaluated under field conditions. The experiment was arranged as a split-plot randomized complete block design. Among the treatments tested, the co-application of F and 500 mg l –1 nGO (FG 4 ) produced the most pronounced response, increasing mean dry herb yield to 4405 kg ha –1 and mean calculated EO yield to 19.5 L ha –1 , approximately 5.8- and 4.6-fold higher than the two-year means of the unfertilized control, respectively. Importantly, the higher EO yield under FG 4 was driven primarily by greater dry leaf biomass rather than by increased EO concentration, identifying biomass accumulation as the central basis of the treatment response. Across nGO doses, organic fertilization generally enhanced yield-related responses more than NPK fertilization, suggesting that fertilization regime modulated basil responses to foliar nGO. FG 4 also showed the highest energy use efficiency (EUE = 3.54), net economic return (USD 11,851 ha –1 ), and benefit-cost ratio (4.32). Overall, these findings suggest that combining foliar nGO with organic fertilization improved biomass production and EO yield in open-field sweet basil, while also supporting more favorable resource-use and economic indicators.