Effects of multiple cropping systems based on spring maize on soil fungal communities in the North China Plain

To explore the impact of multiple spring maize cropping systems on soil quality in the North China Plain, we used DNA Illumina high-throughput sequencing to study fungal community diversity in the 0–20 cm topsoil layer of six cropping systems based on field experiments. The results showed that: 1) Compared with spring maize monocropping (MM, control), the multiple cropping systems double-cropping systems of winter wheat-summer maize (MW), spinach-spring maize (MSp), rye-spring maize (MR), and relay intercropping systems of pea/spring maize (MP), and potato/spring maize (MPo) increased the diversity of soil fungal communities (P<0.05), and the Shannon index by 12.18%, 12.17%, 10.37%, 11.69%, and 8.44%, respectively, compared with MM. However, there was no significant difference among all cropping systems for the soil fungal richness index. 2) The dominant phyla in these cropping systems were Ascomycota, Mortierellomycota, Basidiomycota, Chytridiomycota, and Rozellomycota; in particular, the relative abundance of Ascomycota was more than 80%. 3) Multiple cropping systems increased the number of beneficial fungi. The potentially beneficial communities at the genus level, such as Mortierella and Metarhizium, were relatively enriched in MR, MW, and MSp; and Metarhizium was particularly abundant in MSp. Pyrenochaetopsis was often considered to increase the disease risk in crops, and the order of relative abundance in the six cropping systems was as follows: MM>MW>MP>MR>MSp>MPo. 4) The FUNGuild function prediction results showed that the cropping systems changed the proportion of soil fungal nutrition types. The sprotroph (26.09%), pathotroph (22.48%), and pathotroph-sprotroph-symbiotroph (26.39%) were the main types in the MM; the sprotroph (29.99%) was the main type in the MW; and the sprotroph (21.11%−27.88%) and pathotrophs (23.74%−30.40%) accounted for a larger proportion in the remaining multiple cropping systems. 5) Correlation analysis showed that soil field water-holding capacity, soil organic matter, and bulk density were the main environmental factors affecting soil fungal community structure in this experiment. In summary, compared with spring maize monocropping, rotating or intercropping spring maize with other crops could significantly increase the diversity of soil fungal communities. Among the multiple systems, the rotation patterns of rye-spring maize, spinach-spring maize and winter wheat-summer maize had good performance in improving soil fungal diversity and enriching beneficial microbiota. In addition, the rotation systems of rye-spring maize and spinach-spring maize reduced the abundance of potentially pathogenic fungi to a certain extent. Therefore, combining the demands of water and land conservation, spring maize rotated with rye or spinach may be a better choice from the perspective of soil microorganisms in the North China Plain.