Optimising foliar nano calcium oxide application for improved growth, yield and post-harvest storability of tomato (Solanum lycopersicum L.)

A pot experiment was conducted to investigate the dose-dependent response of tomato (Solanum lycopersicum L.) to foliar application of nano calcium oxide (nano CaO). The study included 13 treatments comprising 11 nano CaO concentrations (100–1500 ppm), a calcium nitrate (CaNO3) treatment and an untreated control, laid out in a completely randomised design (CRD) with 3 replications. Foliar sprays were applied at 30 and 45 DAT. Most traits differed significantly (p < 0.001), showing a hormesis-type response with optimum performance at 600 ppm nano CaO. The 600 ppm treatment consistently produced the tallest plants, highest dry weight, soil plant analysis development (SPAD) values, fruit size, yield (2.23 kg plant-1), shelf life (14.5 days) and fruit firmness (3.21 kg cm-2), while recording the lowest percent of physiological loss in weight (10.1 after 12 days). Compared with calcium nitrate, nano CaO at 600 ppm increased yield by 18.62 % using less than one-third of the calcium concentration. Quadratic regression predicted an optimum nano CaO concentration of 550–635 ppm, corroborating the observed optimum, while correlation analysis identified fruit volume and plant dry weight as the strongest predictors of yield and post-harvest storability. These findings indicate that foliar application of nano CaO at approximately 600 ppm can improve tomato growth, yield and postharvest storability at a substantially lower calcium concentration than calcium nitrate, while the decline in performance at higher concentrations emphasises the need for dose optimisation.