ENHANCING PRODUCTIVITY AND FRUIT QUALITY OF VALENCIA ORANGE TREES USING FOLIAR APPLICATION OF NANO-SILICON, SPIRULINA AND VERMICOMPOST TEA UNDER SALINITY STRESS CONDITIONS

Abstract

This study was conducted in a private citrus orchard located at Wady El-Mollak region, Abo-Hammad District, Sharkia Governorate, Egypt over two successive seasons, 2022/2023 and 2023/2024,on 16-year-old Valencia orange (Citrus sinensis L. Osbeck) trees budded on sour orange rootstock and grown in sandy soil with a spacing of 4 ×6 meters under a drip irrigation system. Thirty-five trees were subjected to seven treatmentsusing natural biological extracts at two concentrations each: spirulina (1.5 and 3 ml L-1) and vermicompost (1.5 and 3 ml L-1), as well as chemical compounds including Nano silicon (600 and 800 mg l-1). The trees were sprayed three times a year, specifically in April, June, and September. In both seasons, the application of Nano silicon at 600 mg L-1 significantly improved yield per tree and per hectare, as well as fruit weight and quantity, compared with the control treatment (water spray). This was followed by the treatments with 800 mg/L of nano silicon and spirulina at both 1.5 ml L-1and 3 ml L-1. These treatments also resulted in superior fruit weight and size compared to vermicompost and the control, with total soluble solids (TSS) values of 13.33% and 13.67%, and TSS/acid ratios of 19.62 and 20.71, indicating enhanced fruit ripeness and sweetness. Additionally, Nano silicon at 800 mg L-1and spirulina at 3 ml L-1produced the highest values for both pulp and peel quality. The lowest performance across most parameters was consistently associated with the control treatment. Overall, both nano silicon and spirulina treatments significantly enhanced various yield quality metrics, fruit parameters, and nutrient content in Valencia orange leaves in sandy soil under salinity stress