Impact of foliar spray of nano-Zn and nano-Cu on biochemical characteristics of guava cv. Allahabad Safeda

Foliar spraying of nanoparticles (NPs) improves the absorption of plant nutrient application compared to traditional soil–root application, and it also enhances the yield and quality of fruits. The present study aimed to evaluate the qualitative effects of foliar sprays of two concentrations of nano-zinc and nano-copper (40 ppm, 60 ppm; 20 ppm, 30 ppm respectively), in comparison to ZnSo4 (recommended by, Punjab Agriculture University, Ludhiana) and control (foliar spray of water) on the guava crop (var. Allahabad Safeda). The experiment was conducted at Lovely Professional University Research farm, Phagwara, Jalandhar (Punjab) by applying a simple randomized block design, with ten treatments applied as T1: control, T2: nano-Zn1, T3: nano-Zn2, T4: nano-Cu1, T5: nano-Cu2, T6: nano-Zn1+ nano-Cu1, T7: nano-Zn1+ nano-Cu2, T8: nano-Zn2 + nano-Cu1, T9: nano-Zn2 + nano-Cu2, T10: ZnSO4 (PAU recommendation) in three replications. The treatments were sprayed two times, first at the flowering stage and second when the fruit reached pea size. The nutrient spray increases the concentration of nutrients in the leaves while also affecting the biochemical parameters. The performance for total soluble solids (9.89°B), total sugars (8.74%), titratable acidity (0.98%), antioxidants (7.49%), firmness (5.71kg/cm2), non-reducing sugars (3.32%), Vitamin-C (268.90mg/100g pulp), pectin content (2.13%), reducing sugars (5.46%), and TSS/acid ratio (10.06) was superior with the application of nano-Zn2 + nano-Cu2 (T9). The application of nano-micronutrients (zinc and copper) in combination is favorable for the quality of guava fruit (Allahabad Safeda).