Synergistic Effects of Nitrogen Fertilization and Plant Growth Regulators on Rice Productivity and Nutrient Uptake under Soil Conditions of the Nile Delta Conditions

The integration of nitrogen fertilization strategies with plant growth regulators (PGRs) offers a robust framework for enhancing rice productivity under intensifying climatic changes. This study examined the combined effects of five nitrogen application rates (0, 40, 80, 120, and 160 kg N/ha) and four PGR treatments (control, cycocel, brassinosteroids BRs, and cytokinin) on the Sakha 108 rice variety over two seasons (2022 and 2023) at the Experimental Farm of Sakha Agricultural Research Station, Sakha, KafrelSheikh, Egypt. A split-plot design with four replications was employed. The nitrogen rates were applied to the main plots, while the plant growth regulator (PGR) treatments were assigned to the subplots. The study evaluated grain yield and its components, as well as nutrient uptake parameters. Results indicated that the highest nitrogen rate, combined with BRs, achieved remarkable grain yields of 13.45 t/ha and 13.68 t/ha in both seasons, respectively. BRs consistently enhanced key agronomic traits compared to other PGRs, confirming their capacity to optimize nitrogen, phosphorus, and potassium use efficiency and to mitigate trade-offs between yield components. These findings underline the potential of integrating PGRs with optimized nitrogen management as a sustainable intensification strategy for rice production under the same experimental conditions.