Document Type : Full Paper

• Fruit Science

Extended Abstract

Introduction

     Olive (Olea europaea L.), a member of the Oleaceae family, is one of the oldest fruit crops domesticated by humans. Although native to Asia Minor and the eastern Mediterranean, its cultivation has expanded widely beyond its natural range due to its remarkable adaptability to diverse climatic conditions and its considerable economic and health-promoting value. Today, the olive is regarded as an important industrial crop worldwide and is cultivated across five continents.

Proper orchard management is a key factor influencing the productivity of tree crops. Foliar fertilization during the growing season is an effective method for supplying essential nutrients to olive trees, particularly under dry conditions and in calcareous soils. The use of agrochemicals to enhance crop productivity has become an integral component of modern agriculture to meet the demands of a growing global population and increasing need for agricultural products. However, the intensive application of synthetic fertilizers has led to soil degradation and nutrient imbalance. Sustainable agriculture therefore relies on strategies that improve nutrient use efficiency and minimize the detrimental environmental effects of agrochemicals.

The use of nanoparticle-based nutrients represents a promising approach to promoting plant performance while supporting sustainable agricultural practices. Due to their extremely small particle size (<100 nm), nanofertilizers possess large surface areas, enabling slow and controlled nutrient release and facilitating efficient uptake through foliar or soil application. These properties provide higher reactivity and improved nutrient availability compared with conventional fertilizers, ultimately enhancing nutrient use efficiency and reducing the negative impacts of synthetic inputs on agricultural ecosystems.

Materials and methods

     The effects of foliar application of silica (Si) and potassium (K) nanoparticles were investigated on the leaf and fruit characteristics of the ‘Zard’ olive cultivar. Potassium nanoparticles (0, 400, and 800 mg L⁻¹) and silica nanoparticles (0, 30, and 60 mg L⁻¹) were sprayed on the trees twice during the growing season—once in early May and again in early July. The study was conducted as a factorial experiment in a completely randomized block design with three replications. Measurements included leaf traits, fruit fresh and dry weight, pulp-to-stone ratio, fruit dimensions, and Si and K concentrations in both leaves and fruits.

Results and discussion

     The foliar application of silica (Si) and potassium (K) significantly influenced most of the studied traits. Both Si and K nanofertilizers enhanced the leaf area index, with the greatest leaf length observed in trees treated with 400 mg L⁻¹ K and 30 mg L⁻¹ Si.

Our results indicated that while both K and Si treatments improved fruit characteristics, the effect of K was more pronounced than that of Si. The simultaneous application of 800 mg L⁻¹ K and 60 mg L⁻¹ Si yielded the most favorable fruit characteristics. Specifically, the application of Si and K, both individually and in combination, increased the fleshy portion of the fruit. The highest pulp-to-stone ratio (3.13) was recorded with 800 mg/L K and 60 mg/L Si, whereas the control group exhibited the lowest ratio (1.8). The greatest fruit dry weight was achieved with the application of 400 mg/L K and 60 mg/L Si.

Foliar application of both Si and K substantially increased their respective content in olive leaves and fruits. While Si content did not differ significantly between leaves and fruits, K content was significantly higher in the fruit than in the leaves.

The results suggest that Si foliar application positively impacts both vegetative and fruit characteristics of olive trees, partly by enhancing essential nutrient absorption and also through its triggering effects on physiological processes within plant cells, such as antioxidant enzyme activity. Therefore, the inclusion of Si foliar spraying in olive fertilization programs is recommended to improve olive performance.

Overall, this investigation revealed strong synergistic effects between Si and K, supporting the recommendation for their simultaneous application to enhance olive tree yield.

Conclusion

     Considering the demand for innovative and environmentally friendly fertilization methods that enhance fruit crop productivity over conventional synthetic chemical fertilizers, this study investigated the effects of potassium (K) and silica (Si) nanoparticles on the vegetative and fruit attributes of the ‘Zard’ olive cultivar.

Both K and Si nanofertilizers significantly supported higher yield in the ‘Zard’ olive cultivar. While individual applications of these nanofertilizers improved olive plant characteristics, the synergistic effects observed when K and Si were applied together proved more beneficial than their separate use, highlighting a strong interaction between these two nutrients.

Our findings demonstrate that applying nutrients in the form of nanofertilizers can enhance olive productivity and optimize nutrient use efficiency. This approach holds the potential to reduce agricultural production costs and minimize nutrient losses from leaching and volatilization.

Author Contributions

1. Erfani-Moghadam, A. Zarei, and A. Shirmardi conceived and planned the experiments. S. Hashemi carried out the experiments. J. Erfani-Moghadam and A. Zarei analyzed data. A. Zarei wrote the first manuscript. J. Erfani-Moghadam, A. Zarei contributed to the interpretation of the results. All authors provided critical feedback and helped shape the research, analysis and manuscript.

Data Availability Statement

Data available on request from the authors.

Acknowledgements

The authors would like to thank Ilam University for the financial support of this research.

Ethical considerations

The authors avoided data fabrication, falsification, plagiarism, and misconduct.

Conflict of interest

The author declares no conflict of interest.