Objective This study aimed to investigate the ameliorative effects of exogenous organic additions on the aggregate stability of Loessal soil.

Method A field-based in-situ bag incubation experiment was conducted. Six types of exogenous organic additions—fruit tree branch biochar (FB), wheat straw biochar (WB), wheat straw (WS), rapeseed straw (RS), chicken manure (CM), and cow manure (CD)—were applied at three rates (1%, 3% and 5%). Soil basic physicochemical properties, the contents of water-stable aggregates in different size classes and aggregate stability indices were determined.

Result All treatments increased soil organic matter, total nitrogen, and electrical conductivity, with the values increasing alongside the application rates. Compared to the 1% and 3% application rates, the 5% rate significantly increased the content of > 0.25 mm aggregates (P < 0.05). Straw amendments (WS, RS) significantly promoted soil particle aggregation and increased the content of water-stable macroaggregates (> 0.5 mm). The mean weight diameter (MWD) of aggregates following different amendments decreased in the order: straws > manures > biochars, with values ranging from 0.18 to 0.52 mm. Regarding application rate, the geometric mean diameter (GMD) increased with higher application rates for wheat straw, rapeseed straw and chicken manure, but decreased for fruit tree branch biochar. Treatments of WS5, CM5 and CD5 significantly decreased the erodibility indices (E_LT) by 29.91%, 28.17% and 23.33%, respectively (P < 0.05), which indicates to enhance aggregate stability.

Conclusion The application of straws at a 5% rate was most effective in increasing the content of > 0.25 mm aggregates and improving aggregate stability. Overall, a higher application rate (5%) of exogenous organic amendments was beneficial for enhancing the stability of soil aggregates in Loessal soil.