Barley remains the fourth most cultivated cereal crop worldwide and is valued for its versatility in malting and brewing, animal feed, human nutrition, and dietary supplements. The identification of genotypes suitable for breeding or specific end-use applications requires multi-environment testing to evaluate agronomic performance, grain quality, and trait stability. In this study, a panel of 50 winter barley genotypes (two-row and six-row) originating from diverse genetic backgrounds was evaluated over three growing seasons (2021–2023) under the environmental conditions of southeastern Romania. Seven traits were analyzed, including three phenological traits (heading time, flowering time and plant height), grain yield, and three quality parameters (thousand-grain weight, protein content, and starch content). Environmental conditions had a strong influence on phenological development and grain yield, whereas grain quality traits showed relatively greater stability, indicating a stronger genetic control. Multivariate analyses (Principal Component Analysis (PCA) and Genotype plus Genotype-by-Environment interaction biplot (GGE biplots)) revealed clear relationships among traits and highlighted contrasting adaptive strategies between the two barley types. In two-row barley, genotypes such as Idra and Sandra combined favorable yield performance with stable grain quality traits and therefore represent promising candidates for breeding programs and large-scale cultivation. In six-row barley, SU-Ellen and LG Zebra showed high productivity and strong starch accumulation, making them valuable genetic resources for yield-oriented breeding, although further improvement in nitrogen use efficiency may be beneficial. The 2022–2023 growing season represented the most restrictive environment, emphasizing the importance of stability under stress conditions. Genotypes located close to the Average Environment Coordination axis (AEC axis) during that season, such as Ametist (six-row) and Lardeya (two-row), may represent promising material for breeding programs targeting drought resilience. Overall, the results expand the phenotypic characterization of winter barley germplasm and identify valuable genetic resources that can support pre-breeding efforts and the development of climate-resilient barley cultivars.

Reducing nitrogen inputs while maintaining grain yield and quality is an important objective for sustainable barley production. This study evaluated 39 winter barley genotypes (20 six-row and 19 two-row) under two N management treatments following pea as the preceding crop during two contrasting growing seasons (2021–2022 and 2022–2023) under rainfed conditions. Both treatments received the same basal fertilization, while the fertilized treatment received an additional 46 kg N ha⁻¹ as urea. Yield response to additional N differed between barley types and growing seasons. In six-row barley, grain yield increased by 5.9% in 2021–2022 but decreased by 4.8% in 2022–2023, whereas two-row barley maintained positive responses of 7.9% and 5.9%, respectively. Additional N consistently increased grain protein content by 17.2–21.7% in six-row and 17.1–19.0% in two-row barley, while starch content decreased in both barley types. NDVI generally increased following additional N application. GGE biplot analysis revealed substantial genotypic variation in performance and response across the four year × nitrogen combinations evaluated at the experimental location. Overall, two-row barley showed a more consistent yield response to additional N across the two growing seasons, while the identified genotypic variation provides useful material for selecting winter barley adapted to reduced N inputs following a legume preceding crop.