Urea and potassium nitrate synergy in sesame cultivation: boosting growth, yield, and antioxidant resilience through tailored nitrogen fertilization

This study aimed to evaluate the effects of different nitrogen sources on sesame ( Sesamum indicum L.) growth, yield, and physiological parameters to identify optimal fertilization strategies for maximizing production. Sesame is a valuable seed plant known for its oil, protein, and antioxidant content. A two-season field experiment (2021 and 2022) was conducted to investigate the impact of eight nitrogen sources, applied at 126 kg N/ha, including two organic sources (urea and thiourea), four nitrate salts (sodium, potassium, calcium, and magnesium nitrates), and two ammonium salts (sulfate and citrate). The experiment followed a completely randomized block design with three replicates. Among the nitrogen sources, urea exhibited superior performance in promoting vegetative growth, nitrogenous compounds, and seed yield. K nitrate emerged as the leading source for enhancing K + and NO 3 − concentrations, capsules number, and oil content. Implementing Na nitrate increased catalase and ascorbate peroxidase activities, while urea enhanced glutathione reductase activity, and Mg nitrate stimulated glutathione-S-transferase activity. Moreover, Mg nitrate demonstrated the highest efficacy in improving Chl b levels and photosystem II photochemical efficiency. Consequently, K nitrate and urea can be considered optimal fertilizers for maximizing sesame production. Although urea resulted in the greatest vegetative growth of sesame, ammonium salts (citrate and sulfate) exhibited the second-highest effectiveness in enhancing most of the evaluated parameters. Compared to the least effective nitrogen source, urea significantly increased Chl b (57.1% vs. K nitrate), carotenoids (58.8% vs. Mg nitrate), amino acids (31.6% vs. K nitrate), nitrogen content (208.8% vs. ammonium citrate), seed yield (62.8% vs. thiourea), and oil production (41.1% vs. ammonium citrate). These results demonstrate that urea and K nitrate are optimal nitrogen sources for maximizing sesame growth and yield, providing farmers with targeted fertilization strategies to enhance productivity and sustainable nutrient management.