Response of the arbuscular mycorrhizal fungi diversity and community in maize and soybean rhizosphere soil and roots to intercropping systems with different nitrogen application rates

Maize (Zea mays L.)/soybean (Glycine max L.) intercropping has been widely practiced in China, because of its effectiveness in improving crop yield and nitrogen utilization efficiency. However, the responses of indigenous arbuscular mycorrhizal fungal (AMF) diversity and communities in rhizosphere soil and roots to intercropping systems with different nitrogen application rates remain unclear. In this study, a field experiment was conducted with split-plot design, and AMF communities in crop rhizosphere soil and roots in monoculture and intercropping systems treated with different levels of nitrogen fertilization were investigated using Illumina MiSeq sequencing. Nitrogen fertilization significantly decreased the AMF alpha-diversity in maize rhizosphere soil, and no significant differences were observed between monocultured and intercropped maize. The Shannon index of soybean rhizosphere soil was significantly higher in intercropping treatments than in monoculture treatments for the corresponding nitrogen levels. The AMF diversity in the roots of maize showed different trends to those in the soil. The dominant genera in the present study were Glomus_f_Glomeraceae, Paraglomus, and Gigaspora, which occupied 55.52%, 9.18%, and 8.20% of the rhizosphere soil and 65.35%, 5.32%, and 17.16% of the roots, respectively. Our study showed that the abundance of the dominant genus, Glomus_f_Glomeraceae in maize soil and roots significantly increased in intercropping treatments compared with monoculture treatments, and it also increased with the increase in nitrogen application levels. In soybean soil and roots, the abundance of Glomus_f_Glomeraceae decreased with the increase in nitrogen application levels. The results of the redundancy and correlations analyses indicated that the changes in the AMF diversity and community in intercropping areas were significantly associated with alterations of the soil total nitrogen and alkali-hydrolysable nitrogen due to the interactions between maize and soybeans in intercropping systems with different nitrogen fertilizer application rates.