Nagy, JánosVad, AttilaMohamed Ibrahim Sidahmed, Hajer2026-01-162026-01-162026https://hdl.handle.net/2437/402978Abstract Field experiments were conducted during the (2022–2023) growing seasons at the Látókép Plant Cultivation Research Centre of the University of Debrecen, Hungary (N 47°33′, E 21°27′), to evaluate the effects of different levels of nitrogen fertilizer, plant density, and sowing date on the yield performance of sweet corn hybrids. The experiments were arranged in a randomized complete block design with a factorial structure and four replications. Yield and phenological traits were assessed for several sweet corn hybrids grown under three nitrogen application rates (100, 150, and 200 kg N ha⁻¹), three plant densities (60,000, 70,000, and 80,000 plants ha⁻¹), and three sowing dates (April 27, May 31, and June 29). Analysis of variance (ANOVA) was applied to determine the significance of treatment effects, while Pearson’s correlation analysis was used to examine relationships among measured traits. The results showed that optimal sweet maize production was achieved at a plant density of 60,000 plants ha⁻¹. Among nitrogen treatments, 100 kg N ha⁻¹ resulted in the highest yield, whereas higher application rates (150 and 200 kg N ha⁻¹) negatively affected yield and were considered inefficient. Sowing date had a significant impact on crop development and yield, with the early sowing date proving most favorable. The hybrid HMC302 achieved the highest yield (29,300 kg ha⁻¹) at the first sowing date, indicating a clear hybrid × sowing date interaction. The Messenger hybrid exhibited excellent adaptability, producing consistently high yields across all tested nitrogen levels, plant densities, and sowing dates (18.550 kg ha⁻¹). In addition, the hybrids Azlan (25,300 kg ha⁻¹) and Spirit (25,200 kg ha⁻¹) also demonstrated strong yield potential. Several hybrids, including GSS6924, GSS649, Azlan, Braveheart, and GSS3071, reached tasselling and silking earlier than others, an important trait for optimizing the cropping cycle and facilitating phased sowing schedules. Overall, the findings highlight the importance of balanced nitrogen management, appropriate plant density, optimal sowing time, and hybrid selection for achieving high and stable sweet corn yield under Hungarian conditions.148enSweet corn, Nitrogen levels, Plant density, Sowing date, Yield, Growth, HybridPhD, doktori értekezésNövénytermesztési és kertészeti tudományokAgrártudományok