Maize/potato intercropping improvs aggregate stability and AMF community diversity in red soil of southern China

Background and Aims Enhancing the stability of soil aggregates can slow down soil erosion. However, the stabilization mechanisms of soil aggregates under different planting patterns and growth stages of maize ( Zea mays L.) and potato ( Solanum tuberosum L.), specifically in relation to the role of arbuscular mycorrhizal fungi (AMF), remains limited in the southwest region of China. The major objective of this study was to determine the changes of soil nutrient content, enzyme activity, glomalin-related soil protein (GRSP) content, AMF community and characteristics of soil aggregates and their interrelationship under different planting patterns and growth stages of maize and potato. Methods A long-term positioning experiment commenced in 2018. Three treatments of maize monoculture, potato monoculture and maize-potato intercropping were established. Non-rhizosphere soil samples were collected at three distinct growth stages for each crop: for maize, these stages were jointing (T1), tasseling (T2), and maturity (T3); for potato, the stages were seedling (T1), peak flowering (T2), and maturity (T3). The analysis focused on changes in soil nutrient content, GRSP content, enzyme activity, and characteristics of soil aggregates. Additionally, the AMF community in both rhizosphere and non-rhizosphere soils was analyzed during the T2 stage of maize and potato. Results The results showed that: (1) Across crop growth periods, the mean weight diameter ( MWD ) of non-rhizosphere soil was highest under maize and potato intercropping at T2 (1.02), followed by potato intercropping at T3 (0.98). (2) Compared with monoculture, the intercropping of maize and potato significantly enhanced the activities of urease (URE), invertase (INV), and catalase (CAT) in the rhizosphere soils of both crops at the T2 stage. Meanwhile, this intercropping pattern also increased the proportion of soil aggregates > 2 mm and the MWD in the non-rhizosphere soils of the two crops, with the magnitude of these improvements ranged from 10.98% to 88.84%. Additionally, potato intercropping increased the relative abundance of unclassified_f__Gigasporaceae and Gigaspora , as well as the Shannon index of the AMF community in rhizosphere soil at T2 stage. (3) During the T2 period, the activities of INV and CAT in rhizosphere soil was significantly higher than in non-rhizosphere soil of maize monoculture and potato intercropping. Conclusion Redundancy analysis revealed the following key finding: During the T1 stage, environmental factors had no significant effect on the stability of non-rhizosphere soil aggregates. At T2, INV, Gigaspora and Diversispora were the primary drivers of non-rhizosphere soil aggregate stability, while CAT and Diversispora dominated the regulation of rhizosphere soil aggregate stability. In the T3 stage, total glomalin-related soil protein (T-GRSP) and CAT were the main factors affecting non-rhizosphere soil aggregate stability. Further structural equation modeling analysis indicated that AMF community diversity, soil organic matter, and T-GRSP directly promoted soil aggregate stability, whereas CAT exerted an indirect positive effect-these patterns were observed during T2 stage. Collectively, these results clarify the mechanism underlying soil fertility improvement under crop diversity.