Compensating Yield Losses Caused by Long-Term Winter Wheat Monoculture Through Crop Protection and Variety Selection

Long-term winter wheat monoculture leads to the deterioration of plant physiological performance and reduced productivity; however, the effectiveness of measures aimed at mitigating these adverse effects has not yet been comprehensively evaluated. The objective of this study was to assess the effects of crop sequence, crop protection intensity, and variety selection on the plant physiological parameters, grain yield, technological grain quality, and mineral composition of winter wheat grain, as well as to determine the extent to which yield losses caused by long-term monoculture can be compensated. The study was conducted during three growing seasons (2022/2023–2024/2025) in a long-term field experiment established in 1967 in Bałcyny, Poland, using a three-factor design with three replications, including two crop sequence systems, three crop protection levels, and two winter wheat varieties. Winter wheat grown in monoculture showed significantly lower leaf greenness index values and grain yield (by 41.4%; p < 0.05) compared with crop rotation. In contrast, monoculture significantly increased grain protein content (by 5.8%), gluten content (by 6.6%), Zeleny sedimentation index (by 20.8%), and the concentrations of nitrogen and zinc in grain (p < 0.05). Crop protection significantly enhanced grain yield; however, it did not completely eliminate the negative effects of long-term monoculture. The variety Revolver produced significantly higher grain yield and leaf greenness index values than Emil, whereas Emil produced grain with significantly higher protein, gluten, and nitrogen contents. The Monoculture Compensation Efficiency (MCE) index showed that crop protection practices enabled the recovery of 63.8–76.2% of yield losses caused by long-term monoculture. The results indicate that integrated crop protection can only partially mitigate the adverse effects of continuous monoculture and cannot replace the benefits associated with the implementation of a proper crop rotation system.