Impact of the Foliar Application of Yeast, Vermicompost Tea, and their Combinations as Biostimulants on Orange Productivity and Fruit Quality

Abstract

Increasing the use of chemical fertilizers to keep pace with the continuous increase in population leads to deterioration of soil fertility, air and groundwater pollution, and the disruption of beneficial microbes. Therefore, there is a necessity to use biostimulants. Biostimulants are valuable for sustainable fruit crop production, boosting growth and plant health. Used with fertilizers, they improve nutrient efficiency and resilience, supporting productivity and environmental goals. Biostimulants promote the blooming, development, and yield of fruit plants. The current study was conducted on navel orange trees cv. Washington grafted on Volkmeriana rootstock during the 2024 and 2025 seasons to investigate the influence of the spraying of yeast extract (YE) at 0.1, 0.2, and 0.3%, vermicompost tea (VCT) at 2, 4, and 6%, and their combinations: 0.1% YE + 2% VCT; 0.2% YE + 4% VCT; 0.3% YE + 6% VCT, compared to trees that were not sprayed. The trees were sprayed three times: before flowering in March, during full bloom, and one month after the second spraying. The results showed that spraying YE, VCT, and their combinations significantly improved vegetative growth parameters, yield, fruit physical and chemical characteristics, and leaf macro- and micronutrient mineral content compared with non-sprayed trees in both seasons.