Effect of foliar application of nano CaO, ZnO and boron on fruit quality and nutrient uptake in tomato (Solanum lycopersicum L.)

A field experiment was conducted during the rabi 2020–21 and 2021–22 at Professor Jayashankar Telangana Agricultural University, Telangana, India to evaluate the effect of foliar applications of nano calcium oxide (CaO), nano zinc oxide (ZnO) and nano boron (B) individually and in combination on tomato cv. US-440. A total of 19 treatments were tested in a randomised block design (RBD) with 3 replications. Foliar sprays were applied at 30 and 45 days after transplanting (DAT). The combined application of nano CaO (600 ppm) + nano ZnO (1000 ppm) + nano B (400 ppm) (T7) significantly improved fruit quality by increasing ascorbic acid (26.41 mg 100 g-1) and titratable acidity (0.51 %), while reducing TSS (3.59 °Brix), total sugars (2.70 %), reducing sugars (2.23 %) and lycopene (5.16 mg 100 g-1). T7 also recorded the highest leaf concentrations of calcium (Ca) (1.89 %), zinc (Zn) (38.20 ppm) and B (42.43 ppm) and the highest fruit Zn content (65.79 ppm), whereas nano CaO (600 ppm) + nano ZnO (750 ppm) + nano B (400 ppm) (T8) recorded maximum fruit Ca (0.85 %) and B (44.17 ppm). Additionally, T7 minimised blossom end rot (2.93 %) and fruit cracking (3.03 %). The superior performance of nanonutrients was attributed to their greater surface area, enhanced absorption efficiency and targeted nutrient delivery. The findings demonstrate the potential of combined nano CaO, nano ZnO and nano B application to improve tomato fruit quality and nutrient use efficiency under field conditions.