Abstract
<title>Abstract</title> <p> Background <italic>Zea mays</italic> L. (maize) is one of the world's most important cereal crops, serving as a staple food, livestock feed, and industrial raw material. It is cultivated across diverse agroecological regions because of its high yield potential, wide adaptability, and multiple ends uses. A two-year field experiment was conducted using a factorial arrangement within a randomized complete block design to evaluate the combined effects of irrigation regime, NPK fertilization, and vermicompost application on the physiological, biochemical, nutritional, and yield-related characteristics of maize ( <italic>Zea mays</italic> L.). Treatments comprised two irrigation regimes (full irrigation at 100% field capacity and deficit irrigation at 70% field capacity), three NPK fertilizer levels (0, 50, and 100% of the recommended rate based on soil analysis), and four vermicompost rates (0, 2, 4, and 6 t ha⁻¹). Results Tukey's HSD test (α = 0.05) revealed significant four-way interactions (Year × Irrigation × NPK × Vermicompost) for all measured traits, indicating that the response of maize was strongly influenced by the combined management practices. The integrated application of 100% recommended NPK with 6 t ha⁻¹ vermicompost consistently produced superior physiological performance, recording the highest chlorophyll content (SPAD = 47.70), relative water content (80.52%), harvest protein yield (964.54 kg ha⁻¹), seed starch (74.22%), phosphorus (0.428%), and potassium (0.360%). These treatments also produced among the highest values for grain yield, biological yield, harvest index, thousand-grain weight, leaf area index, and other productivity-related traits evaluated in the experiment. Compared with the unfertilized control, the optimum treatment increased SPAD, harvest protein, seed starch, phosphorus, and potassium by 84.6%, 330.0%, 14.0%, 41.7%, and 42.9%, respectively, while reducing relative water deficit by 47.3%. Nitrogen concentration and crude protein content reached their maximum values (1.656% and 10.35%, respectively) under full irrigation with 100% recommended NPK, indicating that adequate water availability favored grain nitrogen accumulation, whereas deficit irrigation combined with integrated nutrient management enhanced overall nutrient use efficiency and protein yield. In contrast, the absence of mineral fertilizer and vermicompost consistently resulted in the lowest values for all physiological, nutritional, and yield traits, regardless of irrigation regime. Seasonal differences between the two experimental years were relatively small compared with treatment effects, demonstrating the stability of integrated nutrient management across years. Conclusions Overall, the results indicate that combining the recommended NPK dose with 6 t ha⁻¹ vermicompost is an effective strategy for improving maize growth, water status, nutrient uptake, grain quality, and productivity under both full and deficit irrigation conditions, thereby contributing to sustainable and resource-efficient maize production. </p>