Tillage–Weed Interactions and Hybrid Effects Drive Maize Yield Stability Under Irrigated Chernozem Conditions

Maize productivity in Southeastern Europe is increasingly affected by climatic variability, necessitating agronomic strategies to maintain yield under irrigated conditions. This study evaluated the effects of conventional tillage, minimum tillage, and no-tillage on maize yield, yield components, and weed dynamics, and analyzed the interaction between tillage intensity and hybrid performance under irrigated cambic chernozem conditions in Southeastern Romania. A three-year field experiment (2023–2025) was conducted as a randomized complete block design with three replications using three maize hybrids (P0900, P0937, and P1441) under sprinkler irrigation. Grain yield, kernel weight per ear, kernel number per ear, thousand-kernel weight, plant density, and weed density were analyzed using ANOVA, linear mixed models, and regression analysis. Grain yield ranged from 10.66 to 11.46 t ha−1 across years, with the hybrid exerting the strongest effect on all productivity parameters. P0900 recorded the highest yield (12.43 t ha−1) and the lowest associated weed density. Weed density increased from 207.44 plants m−2 under conventional tillage to 266.11 plants m−2 under no-tillage and was negatively associated with yield components and grain yield. Significant tillage × weed-density interactions indicated steeper productivity declines in reduced-tillage systems, particularly no-tillage. The results suggest that the agronomic performance of conservation-oriented tillage systems under irrigation depends strongly on hybrid adaptability and effective weed-management strategies.