Objectives We investigated the impacts of returning wheat straw combined with distinct tillage practices on the annual productivity and nitrogen (N) utilization efficiency of a wheat-maize rotation system, as well as on soil N storage dynamics. The objective was to identify an optimal straw management strategy for this system.
Methods A long-term field trial was established in Jinan City, Shandong Province, in 2012, employing a winter wheat-summer maize rotation. The conventional practice (CK) served as the control, involving the return of both wheat and maize straw post-harvest, followed by rotary tillage before wheat sowing and no-tillage before maize planting. The experimental treatments included returning only wheat straw with deep tillage (DT), rotary tillage (RT), or no-tillage (NT). During the 2021−2023 harvest seasons, plant samples were collected to assess biomass, N content, and yield. Soil samples were simultaneously obtained across the 0−100 cm profile at 20 cm intervals to determine total N content, enabling calculations of apparent N loss and N use efficiency (NUE).
Results Compared to CK, the RT treatment significantly enhanced wheat, maize, and annual yields over two years, with increases of 4.4%, 5.4%, and 5.1%, respectively. Conversely, the DT treatment reduced yields in 2021 but had no significant impact in 2022, while the NT treatment had no significant effect on wheat yield but decreased maize and annual yields by 3.8% and 4.7%, respectively. Returning only wheat straw reduced soil N input by 33.1% compared to returning straw in both seasons. The RT treatment significantly increased annual crop N uptake by 5.2% relative to CK, whereas DT and NT treatments decreased it by 5.3% and 5.1%, respectively. Soil N storage under RT was 51.9% lower in the 0−20 cm layer but 34.7% and 56.7% higher in the 20−40 cm and 40−60 cm layers compared to CK. Moreover, RT exhibited 36.2% and 63.5% higher N storage in the 0−20 cm layer than DT and NT, respectively, while being 31.3% and 45.7% lower in the 20−40 cm layer. Annual N loss under DT, RT, and NT was significantly lower than CK, with RT showing the greatest reduction (67.6% over two years), followed by DT (43.9%) and NT (42.0%). RT increased aboveground N uptake by 10.4% compared to CK, whereas DT and NT decreased it by 5.3% and 5.1%, respectively. Under single-season straw return, DT, RT, and NT treatments significantly improved aboveground NUE compared to CK, with RT demonstrating the highest increase (37.0%), significantly exceeding DT (16.2%) and NT (12.6%).
Conclusions Returning wheat straw in combination with rotary tillage enhances the annual yield of wheat and maize, promotes plant N uptake, increases soil N storage, and reduces N loss in farmland, thereby achieving a synergistic improvement in annual yield and N utilization efficiency. This practice is recommended as an effective annual straw management strategy for intensive wheat-maize cropping systems in the Huang-Huai-Hai region.
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