Variations in Soil Nitrogen Availability and Crop Yields under a Three-Year Annual Wheat and Maize Rotation in a Fluvo-Aquic Soil

Optimum tillage practices can create a suitable soil environment, and they improve the soil nutrient status to ensure crop development and yield. In this study, we evaluated the influences of six tillage practices on soil nutrients and maize yields from 2017 to 2019 in fluvo-aquic soil in the North China Plain. The field experiment was carried out by a split design with rotary tillage (RT) and deep tillage (DT) in wheat season in the main plot and no-tillage (NT), subsoiling between the row (SBR), and subsoiling in the row (SIR) in maize season in the subplot. The results showed that the soil nutrient content was higher under the treatments with rotary tillage in the wheat season in the 0–20 cm soil layer, while in the 20–40 cm soil layer, the soil nutrient content was higher under the treatments with deep tillage in the wheat season. The integrated principal component scores indicated that the soil nutrients had improved in the second year. The ecosystem multifunctionality (EMF) index was higher with the treatments with rotary tillage in wheat season in the 0–20 cm soil layer, while it was the highest under DT-SIR at 20–40 cm. Correlation analysis showed that the soil EMF index correlated significantly (p < 0.05) with the soil nutrient content mainly in the 0–40 cm soil layer. The higher maize yield was under the treatments with deep tillage compared to that under the treatments with rotary tillage in the wheat season. The yield-increasing effect was higher under the treatments with subsoiling than those utilizing no-till in the maize season, with the highest average yield of 13,910 kg hm(−2) in the DT-SIR during the three years. Maize yield was strongly correlated with nutrients in the subsoil layer. The higher yield stability was found under RT-NT. To sum up, during the three-year experiment, rotary tillage in the wheat season combined with subsoiling in the maize season improved the soil nutrient content and the EMF index in the 0–20 cm layer, while the combination of deep tillage in the wheat season and subsoiling in the maize season improved those indices in the 20–40 cm soil layer, and increased the maize yield, the best one was under DT-SIR.