Cultivar-specific irrigation responses of bell pepper (Capsicum annuum) in high tunnel and open-field environments

Introduction Efficient irrigation management and cultivar selection are critical for improving water productivity and sustaining yield stability in protected vegetable production systems under increasing climatic variability. High tunnel (HT) environments can modify temperature and evapotranspiration dynamics, thereby influencing crop responses to irrigation management. This study aimed to identify bell pepper cultivars with high productivity and stable performance under deficit irrigation strategies in contrasting HT and open field (OF) environments. Methods A two-year field study was conducted during the 2022 and 2023 growing seasons to evaluate the performance of Bell pepper cultivars under three irrigation strategies in HT and OF production systems. Irrigation treatments included 10% management allowable depletion (MAD), 30% MAD, and conventional time-based irrigation scheduling. Yield components, marketable and unmarketable yield, fruit number, and fruit size attributes were measured to assess cultivar productivity, irrigation responsiveness, and performance stability across environments. Results The HT environment moderated diurnal temperature fluctuations while maintaining consistently higher minimum temperatures than the OF environment, with seasonal increases ranging from 1.1 to 5.2 °C and maximum temperatures occasionally reaching 40.7 °C. Significant cultivar × irrigation interactions were observed under HT conditions for total yield, marketable yield, and fruit number, indicating differential cultivar responses to soil moisture management. Cultivars such as Early Sunsation and King Arthur produced greater yields under MAD-based irrigation treatments, demonstrating strong responsiveness to optimized soil water depletion and improved production efficiency under deficit irrigation. Conversely, cultivars including Ninja and X3R Red Knight maintained relatively stable yields across irrigation treatments, suggesting greater physiological stability and adaptability to reduced irrigation inputs. Under OF conditions, irrigation treatments did not significantly influence yield parameters, likely because rainfall and lower evaporative demand minimized differences in soil water availability among treatments. However, cultivar effects significantly influenced unmarketable yield, primarily due to physiological disorders such as sunscald and blossom-end rot. Fruit size characteristics remained relatively stable across irrigation treatments and were predominantly determined by genetic factors. Discussion The results demonstrated substantial genotypic variation in irrigation responsiveness and water-use efficiency among bell pepper cultivars under protected cultivation. Deficit irrigation strategies based on MAD thresholds improved irrigation efficiency without compromising productivity in adapted cultivars, particularly under HT conditions where elevated thermal demand increased the importance of precise soil moisture management. Cultivars exhibiting both high productivity and stable performance under reduced irrigation represent promising genetic resources for sustainable protected vegetable production. Integrating cultivar selection with precision irrigation management may therefore enhance yield stability, resource-use efficiency, and climate resilience in HT bell pepper production systems.