Foliar application of biostimulants and silicon enhances yield and fruit quality of ‘Page’ mandarin via altering physiochemical properties

Abstract

Background: In the present research, the effects of foliar application of seaweed extract, fulvic acid, and potassium silicate on leaf mineral contents, chlorophyll content, fruit yield, and quality, as well as physiochemical attributes of ‘Page’ mandarin fruits were evaluated. Results: Leaves of trees fed with seaweed extract, fulvic acid, and potassium silicate accumulated greater concentrations of N (15.09–22.16%), P (20–120%), K (17.02–46.80%), Ca (1.69–32.76%), Mg (26.31–84.21%), Zn (199.87–261.76%), Mn (79.92–139.04%), and Fe (59.12–148.65%) than those unfed. Mandarin trees fed with the nutrient solutions, especially seaweed extract, had higher chlorophyll a (10.61–29.20%) and total chlorophyll (8.75–24.37%) contents. Applying the nutrient solutions, especially seaweed extract, increased yield (23.86–48.87%), fruit juice (7.86–16.35%), and firmness (3.47–19.58%), but reduced the pulp (23.16–39.64%) of fruits. Moreover, fruits of mandarin trees fed with the nutrient solutions and especially seaweed extract showed a greater level of total soluble solids (TSS) (26.03–41.58%), total soluble solids/titratable acidity (TSS/TA) (16.99–32.70%), color index L* (5.68–10.88%), color index a* (54.07–100.90%) and color index b* (30.02–58.80%), vitamin C (41.04–84.84%), total phenol (26.76–64.78%), carotenoid (130.76–167.92%), antioxidant activity (3.56–12.87%), as well as the activity of guaiacol peroxidase (GPX) (12.03–44.39%) and catalase (CAT) (26.92–53.84%), ascorbate peroxidase (APX) (77.81–103.34%), and superoxide dismutase (SOD) (11.32–38.36%) enzymes. Conclusion: The study findings evidenced that foliar application of seaweed extract, fulvic acid, and potassium silicate has a high potential for improving fruit yield and quality of mandarin.