Influence of Preceding Crops and Fertilization Strategies on Wheat Performance and Disease Dynamics

Mineral fertilization is crucial for maximizing wheat yield, ensuring optimal nitrogen and phosphorus supply according to plant development, pedoclimatic conditions, and previous crops, with a balanced N:P ratio being decisive for productivity. This study, conducted at ARDS Turda during 2020/2021–2024/2025, evaluated the long-term effects of nitrogen and phosphorus fertilization on the yield, grain protein content, and foliar disease incidence of winter wheat grown after maize and soybean. The experimental design was polyfactory, in randomized blocks, including 25 variants and 6 repetitions, according to the uninterrupted protocol used since 1967, winter wheat being cultivated after maize for grain and soybean. Phosphorus (0–160 kg P2O5 ha−1) was applied in autumn, while nitrogen (0–160 kg N ha−1 after maize and 0–120 kg N ha−1 after soybean) was split 50% in autumn and 50% in spring. Results indicate that wheat yield is strongly influenced by nitrogen–phosphorus interactions and climatic conditions, with nitrogen increasing yield by 450–2700 kg·ha−1 and maximum yields of 7600–7828 kg·ha−1 achieved at N120 with higher phosphorus rates. Grain protein content (14.96%) was high at N120 dose, while foliar disease incidence and severity were low at minimal fertilization and rose with intensified mineral nutrition.