Objectives To explore the influence of maize and peanut co-ridge intercropping and phosphorus application on soil aggregate stability, and to provide a scientific basis for optimizing strip composite planting technology, further improving soil structure and rational fertilization.

Methods From 2010 to 2022, experiments were conducted at the experimental farm of Henan University of Science and Technology. Maize variety Zhengdan 958 and peanut variety Huayu 16 were used as test materials. Two planting modes, flat intercropping of maize and peanut (FIC) and co-ridge intercropping of maize and peanut (RIC), along with two phosphorus levels, P₂O₅ 0 kg/hm² (P₀) and P₂O₅ 180 kg/hm² (P₁₈₀), were set. After the harvest of summer crops in October 2022, soil samples from the 0−20 cm soil layer were collected, and the particle size distribution and stability of soil aggregates were analyzed using three methods: dry sieving, wet sieving, and Le Bissonnais (slow wetting (SW), wet stirring (WS), and fast wetting (FW)).

Results Compared with flat intercropping (FIC), the proportion of aggregates larger than 0.25 mm (R_0.25) in the co-ridge intercropping (RIC) treatment increased by 0.2% to 6.0%, the mean weight diameter (MWD) of soil aggregates increased by 1.1% to 12.9%, and the geometric mean diameter (GMD) increased by 2.8% to 14.3%. Compared with P₀, the P₁₈₀ treatment increased the proportion of aggregates larger than 0.25 mm (R_0.25) by 2.0% to 13.3%, increased the MWD of aggregates by 4.2% to 22.7%, and increased GMD by 8.3% to 32.6%. The order of MWD, GMD, and R_0.25 of soil aggregates was P₀FIC<P₀RIC<P₁₈₀FIC<P₁₈₀RIC. In the Le Bissonnais method, the MWD order of soil aggregates was SW>WS>FW. Additionally, the mean weight diameter measured by the dry sieving method (MWD_D) was significantly positively correlated with that measured by the SW (MWD_SW) and WS (MWD_WS) methods (P<0.001). The mean weight diameter measured by the wet sieving method (MWD_W) was positively correlated with that measured by the FW (MWD_FW) method (P<0.001).

Conclusions Maize-peanut ridge intercropping (RIC) increased the content of soil aggregates and enhanced the stability of the aggregates. Phosphorus application further improved soil structure stability. The results of this study provide a reference for better understanding farmland soil structure and soil aggregate stability under different intercropping conditions.