Effects of nitrogen fertigation and irrigation management on onion (Allium cepa L.) growth and bulb yield under open-field conditions

Purpose: Efficient nitrogen (N) and water management are essential for sustainable onion (Allium cepa L.) production, particularly under changing climatic conditions and resource limitations.This study investigated the effects of N fertilization and irrigation levels on soil water status, soil inorganic N dynamics, plant growth, and bulb yield of onion under open-field conditions.Methods: A split-plot field experiment was conducted during the 2023 -2024 growing season using four N fertilization levels (0N, 1/3N, 2/3N, and 1N) and four irrigation levels (25%, 50%, 75%, and 100% of crop water requirement).Irrigation scheduling was based on solar radiation and rainfall, and irrigation was applied through a drip fertigation system.Soil water matric potential, soil inorganic N, plant growth, and bulb yield were determined.Results: Soil water matric potential maintained at adequate moisture levels across treatments throughout the growing season.N fertigation significantly increased soil inorganic N availability, vegetative growth, biomass accumulation, bulb development, and yield, whereas irrigation had limited overall effects under the adequate soil moisture conditions.Soil inorganic N gradually declined during crop growth, indicating effective plant uptake without excessive residual accumulation.Onion yield increased progressively with increasing N application, reaching a maximum of 8271.8 kg 10a -1 under the 1N treatment.Two-way ANOVA indicated that N fertigation was the primary factor regulating onion growth and productivity under the experimental conditions.Conclusions: These findings suggest that N availability is the primary factor governing onion productivity under adequate soil moisture conditions.Solar radiation-based irrigation management effectively maintained favorable soil moisture conditions and minimized water stress throughout the growing season.This integrated irrigation and N fertigation management provides a climate-adaptive and resource-efficient strategy for sustainable onion production.