Optimized Irrigation and Nitrogen Fertilization Enhance Sorghum Yield and Resilience in Drought-Prone Regions

Sorghum [<i>Sorghum bicolor</i> (L.) Moench] is a vital cereal crop in semi-arid regions, but its productivity is often limited by water scarcity and inefficient nitrogen (N) management. While previous studies have explored the individual effects of irrigation and N application, limited research has examined their combined influence on sorghum growth, phenology, and yield. This study aimed to assess the impacts of four irrigation levels (0, 75, 100, and 125% of irrigation as I₀, I₇₅, I₁₀₀, and I₁₂₅) and four N application rates (0, 90, 180, and 360 kg N ha^-1 as N₀, N₉₀, N₁₈₀, and N₃₆₀) on sorghum performance to identify optimal water and nutrient management strategies. A field experiment was conducted over two growing seasons, measuring plant height, number of leaves, panicle length, flowering percentage, visual maturity rating, biomass, and grain yield using a split-plot design, with irrigation as the main factor and N rates as subplots with three replications. Key findings revealed that irrigation and N application significantly influenced plant height, number of leaves, panicle length, biomass, and grain yield. The highest plant height (58.06 cm), number of leaves (10.25), and panicle length (26.60 cm) were observed under I₁₂₅. Compared to the I₀ treatment, the increase in visual maturity rating in I₇₅ and I₁₀₀ was 64.91% and 249.70%, respectively. The highest biomass (3.25 t/ha) was observed for treatment I₁₂₅, while the highest grain yield (2.40 t/ha) was for I₁₀₀. Compared to N₀, treatments N₉₀, N₁₈₀, and N₃₆₀ increased grain yield by 64.8, 66.4, and 81.6%, respectively. The Pearson correlation analysis revealed significant positive relationships among key crop growth, phenology, and yield traits. The maturity rating correlated highest with flowering percentage (0.76). The response to N application was more pronounced under well-watered conditions, with the steepest grain yield increase observed under N₃₆₀. In water-limited conditions, higher N rates did not improve yield. Based on these results, applying irrigation at 100% of the crop water requirement and at least 180 kg N ha^-1 is recommended to enhance sorghum resilience, resource-use efficiency, and sustainable production, particularly in water-scarce regions.