Impact of Foliar Spray of Liquid Nano DAP Formulation on Physiological and Biochemical Changes in Rice

The commercially available Gromor nano DAP (nDAP) was used for this study, as it fulfilled the stipulated specifications of FCO, such as hydrodynamic and physical sizes (<100 nm), pH, zeta potential, viscosity, specific gravity, and nutrients. The mode of action, physiological, biochemical, and nutritional changes in nDAP and conventional DAP (cDAP) sprays were studied in rice during two crop seasons (Rabi 2023 and Kharif 2024). The SEM images after the foliar spray have shown that nDAP gets absorbed by leaves within 2 h in comparison to cDAP (>12 h), indicating rapid absorption. After entry into the plant system, the activities of N assimilatory enzymes, such as nitrate reductase (NR), glutamine synthetase (GS), glutamate synthase (GOGAT), and acid phosphatase (APS), were higher consistently by 12.5, 33.5, 6.31, and 18.7% in nDAP in comparison to cDAP-sprayed rice plants, indicating rapid N and P assimilation. As a result, nDAP-sprayed plants had significantly higher photosynthetic rates (3.4–7.7%), stomatal conductance (18–23%), transpiration rate (6–7%), and SPAD (12.9–16.6%) than cDAP- sprayed plants. Nano DAP-sprayed rice plants had higher N and P contents in critical growth stages. Overall, the data suggest that nDAP gets absorbed in the plant system rapidly and orchestrates the physiological processes and nitrogen and phosphorous assimilatory pathways that collectively contribute to the improved growth and nutritional responses. This is one of the early reports suggesting insights involved in nDAP-sprayed plants leading to nutrient status.