Maize/soybean intercropping facilitated phosphorus solubilization as regulated by Arbuscular Mycorrhizal fungal and bacterial communities in red soil

Ling Qian¹Li Tang¹Jingxiu Xiao¹Lili Mao²Ping Lv³Faming Zhang⁴Yi Zheng^1*

• ¹Yunnan Agricultural University, Kunming, China
• ²College of agriculture and horticultural technology,Yunnan, kunming, China
• ³Kunming Customs Technology Cente, kunming, China
• ⁴Yunnan Open University, Kunming, China

Arbuscular mycorrhizal fungi (AMF) are key regulators for phosphorus (P) cycling in agricultural systems. However, under intercropping conditions, the mechanisms through which AMF hyphae and spores recruit specific bacterial taxa and synergistically solubilize insoluble P in red soils remain poorly understood. Through a greenhouse pot experiment with maize/soybean intercropping (IMS), this study investigated how the symbiotic relationship between AMF and crops varies across a gradient of P fertilizer levels (P0 to P250). It aimed to identify the P level that optimizes this symbiosis and to elucidate the regulatory mechanism by which interactions between AMF and phosphate-solubilizing bacteria (PSB) drive P activation. The mycorrhizal colonization rate of maize and soybean roots, together with the hyphal length density (HLD) and spore density (SD) in rhizosphere soil, exhibited a phosphorus hump-shaped response to increasing P fertilizer inputs, peaking at the P150 treatment. IMS enhanced mycorrhizal colonization rate, HLD, and SD, and also enriched Glomus_f_Glomeraceae along with eight key bacterial taxa (e.g., Sphingomonas, unclassified_f_Micrococcaceae, Streptomyces). The relative abundance of Glomus_f_Glomeraceae peaked under the P150 treatment, correlating with the optimal AMF-crop symbiosis. Cross-domain co-occurrence network analysis showed a higher proportion of positive associations between AMF and bacteria in the intercropping system than in the monoculture. This study demonstrates that IMS enhances P activation in red soils by strengthening the synergistic interactions between AMF and PSB, thereby providing a theoretical basis for improving P use efficiency and conserving mycorrhizal function. Our findings offer a novel microbial perspective for developing sustainable management strategies in red soil agroecosystems.