## 2 Materials and Methods
### Analysis Methods  
Genomic DNA was extracted from soil samples using the Cetyltrimethylammonium Bromide (CTAB) method. The bacterial 16S rRNA gene was amplified using primers 27F (5\({}^{\prime}\)-AGAGTTTGATCMTGGCTCAG-3\({}^{\prime}\)) and 1492R (5\({}^{\prime}\)-GGTTACCTTGTTACGACTT-3\({}^{\prime}\)), while fungal ITS regions were amplified with primers ITS1F (5\({}^{\prime}\)-CTTGGTCATTTAGAGGAAGTA-3\({}^{\prime}\)) and ITS4 (5\({}^{\prime}\)-TCCTCCGCTTTATGATAGC-3\({}^{\prime}\)) [30; 31; 32]. PCR amplification was performed in a 50 \(\mu\)L reaction system under the following conditions: initial denaturation at 94 \({}^{\circ}\)C for 4 min, denaturation at 94 \({}^{\circ}\)C for 50 s, annealing at 52 \({}^{\circ}\)C for 1 min, and extension at 72 \({}^{\circ}\)C for 1.5 min, followed by a final extension at 72 \({}^{\circ}\)C for 14 min. Fluorescence spectrophotometry was applied to quantify DNA, and the quality of electrophoresis completion of enriched fragments was assessed using an Agilent 2100 Bioanalyzer (Agilent Technologies, Inc., Santa Clara, CA, USA). The DNA library fragment size and distribution patterns were investigated and then sequenced in high throughput on the Illumina MiSeq platform (Illumina, Inc., San Diego, CA, USA) [33]. Soil organic carbon (SOC) concentration was determined using the potassium  
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Total** & **Total** & **Total** & **Total** & **Hemi** & **Cellulose** & **Lignin** \\
**Carbon** & **Nitrogen** & **Phosphorus** & **Potassium** & **Cellulose** & **Cellulose** & **Lignin** \\ \hline
41.78 \(\pm\) 0.10 & 0.92 \(\pm\) 0.04 & 0.15 \(\pm\) 0.00 & 1.11 \(\pm\) 0.01 & 23.45 \(\pm\) 0.41 & 37.25 \(\pm\) 0.23 & 2.85 \(\pm\) 0.03 \\ \hline \end{tabular}  
The values represent means \(\pm\) se (\(n=3\)).  
\end{table}
Table 1: The nutrient content of the corn straw used in the experiment (%).  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**OM** & **TN** & **AN** & **AP** & **AK** & **pH** \\
**(g kg\({}^{-1}\))** & **(g kg\({}^{-1}\))** & **(mg kg\({}^{-1}\))** & **(mg kg\({}^{-1}\))** & **(mg kg\({}^{-1}\))** & **(mg kg\({}^{-1}\))** & **pH** \\ \hline
20.10 \(\pm\) 0.03 & 1.54 \(\pm\) 0.01 & 121.84 \(\pm\) 0.20 & 26.34 \(\pm\) 0.04 & 134.24 \(\pm\) 0.49 & 6.11 \(\pm\) 0.02 \\ \hline \end{tabular}  
Abbreviations: OM (organic matter), TN (total nitrogen), AN (alkali hydrolyzable nitrogen), AP (available phosphorus), AK (available potassium). The values represent means \(\pm\) se (\(n=3\)).  
\end{table}
Table 2: Initial physical and chemical properties of soil.  
dichromate heating method [34]. Fresh soil samples were extracted using 0.05 mol L\({}^{-1}\) K\({}_{2}\)SO\({}_{4}\) by shaking for 30 min and subsequently filtered through qualitative filter paper. The resulting filtrate was analyzed for dissolved organic carbon (DOC) content using a TOC analyzer (Liqui TOC II, Elementar, Langenselbold, Germany) [35]. Readily oxidizable organic carbon (ROC) was determined by the potassium permanganate oxidation method [36]. Microbial biomass carbon (MBC) concentration was analyzed by the chloroform fumigation and extraction method [37]. In each plot, to avoid border effects, three random quadrates each covering 9 m\({}^{2}\) were selected to determine maize grain yield, measured by adjusting the grain moisture content to 14% [38].