Objectives We studied the fungal community structure and diversity in different soil aggregate particle sizes under intercropping conditions. We aimed to understand the beneficial effect of intercropping from the perspective of microbial properties.
Methods The long-term positioning experiment started in 2013 and was located at the experimental base of Yunnan Agricultural University. The maize and soybean test cultivars were Qiaodan 6 and Diandou 7. The cropping pattern treatments were soybean and maize intercropping (MD), maize monoculture (MM), soybean monoculture (DD), and fallow (CK). At the maize tasselling stage in 2021, 0−20 cm soil samples were collected, and the wet sieving method was used to screen the soil aggregates into 2−1 mm, 1−0.25 mm, and <0.25 mm particle size groups. The percentage of each aggregate group in the total soil aggregate and their mean weight diameter (MWD) were determined. The organic carbon, total N, and available N, P, and K were analyzed in each group. The fungal community structure was analyzed using Illumina MiSeq Next Generation sequencing.
Results MD (P<0.05) increased the percentage and MWD in 2−1 mm aggregates, the organic carbon content in 2−1 mm aggregates, anf alkali-hydrolyzed N in 1−0.25 mm and <0.25 mm aggregate. All the DD, MM, and MD treatments increased the Chao1 index and OTU number in 2−1 mm and 1−0.25 mm aggregates than CK. The relative abundance of Basidiomycota in 2−1 mm and 1−0.25 mm aggregates in MD was 85.7% and 133.3% higher than in DD, and 194.1% and 69.7% higher than in MM, respectively. The relevant abundance of Chytridiomycotal in MD was 20.0% and 333.3% higher than in MM, Chaetomium in 2−1 mm, 1−0.25 mm, and <0.25 mm aggregates in MD was 68.7%, 80.0%, and 53.2% higher than in MM, respectively. MD had 60.0% and 72.4% higher relative abundance of Mortierellomycota and Mortierella than MM in 2～1 mm aggregate. PCoA analysis showed that the fungal community significantly differed among particle sizes and planting modes. RDA showed that soil organic carbon, available N, total N, and α-diversity index were significantly correlated. The heatmap analysis showed that basidiomycetes were (P<0.05) correlated with soil total N, alkali-hydrolyzed N, and organic carbon.
Conclusions Soil organic carbon, total N and alkali-hydrolyzed N are the main drivers of variation in the structure and diversity of the fungal community. Compared with monoculture, intercropping promoted the formation and stability of macroaggregates. It also increased soil organic carbon, available N, dominant fungi and diversity of macroaggregates. Thus, soybean-corn intercropping pattern changes the distribution of aggregates, along with changes in soil fungal community and diversity, which is conducive to improving soil microenvironment, quality, and health.
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