Application of ZnO NPs, SiO2 NPs and Date Pollen Extract as Partial Substitutes to Nitrogen, Phosphorus, and Potassium Fertilizers for Sweet Basil Production

Abstract

The reduction in mineral fertilizer usage is crucial to the production of medicinal and aromatic products for safety and health purposes. Presently, nanotechnology and the utilization of natural extracts have been extensively studied due to their significant contribution. Ocimum basilicum is commonly employed for various medicinal and aromatic applications. Therefore, randomized complete block design field experiments containing 10 treatments were conducted during the 2021 and 2022 seasons to investigate the effect of nanoparticles (NPs) of ZnO (1.5 and 2.0 g/L) and SiO2 (100 and 150 mg/L) and date palm pollen extract (DPPE) at 10 and 20 g/L either alone or in combination with the ¾ or ½ NPK recommended dose (RD). The NPK RD was served as a control treatment on basil plant production in each season. The effectiveness of ZnO NPs, SiO2 NPs, and DPPE for the decrease in NPK utilization was evaluated. Meanwhile, the most effective treatment for vegetative traits (except for plant height), essential oil %, and yield was ½ NPK RD + 20 g/L DPPE + 2.0 g/L ZnO NPs. Such a treatment increased the branch number/plant, main stem diameter, relevant chlorophyll content, fresh weight/plant, dry weight/plant, essential oil %, and essential oil yield/plant by 21.00 and 9.94%, 58.70 and 40.00%, 20.69 and 15.83%, 68.83 and 58.28%, 48.70 and 56.16%, 45.71 and 35.53%, and 113.22 and 110.32% over the control in the two seasons, respectively. For total phenol and antioxidant activity, the most effective treatments were the ¾ NPK +1.5 g/L ZnO NPs and ½ NPK +2.0 g/L ZnO NPs, respectively. Simultaneously, essential oil composition (with their compound numbers identified (11–29 for control and ¾ NPK RD + 1.5 g/L ZnO NPs)) and the percentage of total compounds, monoterpene hydrocarbons, sesquiterpene hydrocarbons, and oxygenated hydrocarbons were varied among the used applications. The major observed compounds (>8%) estragole, methyl eugenol, linalool, cineole, and caryophyllene were found in different treatments. Thus, the findings of this study indicate the favorable utilization of ZnO NPs, SiO2 NPs, and DPPE in reducing the application of NPK, which may present a novel strategy and beneficial approach.