Combined application of chitosan-boron and chitosan-silicon nano-fertilizers with soybean protein hydrolysate to enhance rice growth and yield

Abstract The effects of chitosan-boron (CS-B) and chitosan-silicon (CS-Si) combined with soybean protein hydrolysate (SPH) on the growth and yield of Rice Department 79 (RD 79) variety plants in a greenhouse were examined. Particle sizes were 331.9 nm (CS-B), 310.4 nm (CS-Si), and 188.5 nm (SPH solution containing CS-B and CS-Si), with zeta potentials of 30.8, 25.3, and −4.7 mV, respectively. Scanning electron microscopy and Fourier transform infrared spectroscopy confirmed the surface morphology and characteristic functional groups of these nano-fertilizers. A nitrogen–phosphorus–potassium (NPK) fertilizer was applied to rice plants at 1 g/pot (full rate) via the soil at 30 and 60 days after transplanting (DAT), and it served as the control group. The other treatments were applied with half-rate NPK fertilizer (0.5 g/pot) at the same time points, combined with a foliar spray (200 mL/plant) of a solution containing CS-B (0.5% w/v), CS-Si (0.1% w/v), and SPH (0.5:2:100 v/v/v ratio) diluted to final concentrations of 1 and 2 mL/L. At 75 DAT, applying half-rate NPK with the 2 mL/L SPH solution containing the CS-B and CS-Si nano-fertilizer significantly increased the canopy diameter (42 ± 2 cm) and plant height (129 ± 3 cm) compared to the full-rate NPK treatment ( p < 0.05). At 118 DAT, this treatment also increased the number of rice grains (215 ± 14 grains) and grain yield per plant (127 ± 16 g) ( p < 0.05). These results suggested that the CS-B and CS-Si nano-fertilizers conjugated with SPH could be a novel technique to enhance RD 79 rice growth and yield by reducing fertilizer usage.