## 3 Results
### Correlation and Multiple Regression of Soil Chemical Properties and the Gene Copy Number  
The correlation and multiple regression analysis indicated a potential relationship between the soil edaphic factors and the gene copy number of the nitrification and denitrification functional genes. The archaeal _amoA_ was significantly and positively correlated \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline
**Treatment** & **Year** & **pH** & **EC** & **OM** & **TN** & **P\({}_{2}\)O\({}_{5}\)** & **K** & **Ca** & **Mg** & **Na** \\  & & **(I:S)** & **dS m\({}^{-1}\)** & **\%** & **\%** & **mg kg\({}^{-1}\)** & & & **cmol kg\({}^{-1}\)** & \\ \hline \multirow{6}{*}{NF} & 2018 & 5.76 \({}^{\text{a}}\) & 0.39 \({}^{\text{b}}\) & 2.46 \({}^{\text{a}}\) & 0.20 \({}^{\text{b}}\) & 30.15 \({}^{\text{ab}}\) & 0.18 \({}^{\text{b}}\) & 5.19 \({}^{\text{b}}\) & 1.20 \({}^{\text{bc}}\) & 0.29 \({}^{\text{b}}\) \\  & 2019 & 5.86 \({}^{\text{a}}\) & 0.55 \({}^{\text{b}}\) & 2.16 \({}^{\text{b}}\) & 0.38 \({}^{\text{a}}\) & 24.23 \({}^{\text{b}}\) & 0.15 \({}^{\text{be}}\) & 5.35 \({}^{\text{b}}\) & 1.28 \({}^{\text{ab}}\) & 0.34 \({}^{\text{a}}\) \\  & 2020 & 5.91 \({}^{\text{a}}\) & 0.44 \({}^{\text{b}}\) & 2.64 \({}^{\text{a}}\) & 0.19 \({}^{\text{b}}\) & 36.14 \({}^{\text{a}}\) & 0.28 \({}^{\text{a}}\) & 6.96 \({}^{\text{a}}\) & 1.37 \({}^{\text{a}}\) & 0.36 \({}^{\text{a}}\) \\  & 2021 & 5.80 \({}^{\text{a}}\) & 0.90 \({}^{\text{a}}\) & 2.11 \({}^{\text{b}}\) & 0.15 \({}^{\text{c}}\) & 28.00 \({}^{\text{ab}}\) & 0.13 \({}^{\text{c}}\) & 5.70 \({}^{\text{b}}\) & 1.13 \({}^{\text{c}}\) & 0.29 \({}^{\text{b}}\) \\ \hline \multirow{6}{*}{NPKCom} & 2018 & 5.95 \({}^{\text{a}}\) & 0.44 \({}^{\text{a}}\) & 3.14 \({}^{\text{a}}\) & 0.25 \({}^{\text{b}}\) & 128.08 \({}^{\text{a}}\) & 0.27 \({}^{\text{b}}\) & 6.37 \({}^{\text{a}}\) & 1.58 \({}^{\text{a}}\) & 0.33 \({}^{\text{a}}\) \\  & 2019 & 6.18 \({}^{\text{a}}\) & 0.71 \({}^{\text{a}}\) & 2.97 \({}^{\text{a}}\) & 0.56 \({}^{\text{a}}\) & 175.19 \({}^{\text{a}}\) & 0.39 \({}^{\text{ab}}\) & 7.24 \({}^{\text{a}}\) & 1.91 \({}^{\text{a}}\) & 0.42 \({}^{\text{a}}\) \\  & 2020 & 6.23 \({}^{\text{a}}\) & 0.55 \({}^{\text{a}}\) & 3.29 \({}^{\text{a}}\) & 0.26 \({}^{\text{b}}\) & 179.84 \({}^{\text{a}}\) & 0.50 \({}^{\text{a}}\) & 7.21 \({}^{\text{a}}\) & 1.66 \({}^{\text{a}}\) & 0.35 \({}^{\text{a}}\) \\  & 2021 & 5.99 \({}^{\text{a}}\) & 1.23 \({}^{\text{a}}\) & 2.90 \({}^{\text{a}}\) & 0.22 \({}^{\text{b}}\) & 141.33 \({}^{\text{a}}\) & 0.53 \({}^{\text{a}}\) & 7.35 \({}^{\text{a}}\) & 1.71 \({}^{\text{a}}\) & 0.31 \({}^{\text{a}}\) \\ \hline \multirow{6}{*}{Com} & 2018 & 5.67 \({}^{\text{a}}\) & 0.47 \({}^{\text{a}}\) & 3.08 \({}^{\text{a}}\) & 0.25 \({}^{\text{b}}\) & 59.86 \({}^{\text{b}}\) & 0.29 \({}^{\text{b}}\) & 5.72 \({}^{\text{b}}\) & 1.27 \({}^{\text{a}}\) & 0.33 \({}^{\text{a}}\) \\  & 2019 & 5.90 \({}^{\text{a}}\) & 0.63 \({}^{\text{a}}\) & 2.95 \({}^{\text{a}}\) & 0.49 \({}^{\text{a}}\) & 59.40 \({}^{\text{b}}\) & 0.40 \({}^{\text{ab}}\) & 6.14 \({}^{\text{b}}\) & 1.41 \({}^{\text{a}}\) & 0.39 \({}^{\text{a}}\) \\ \cline{1-1}  & 2020 & 5.19 \({}^{\text{a}}\) & 0.42 \({}^{\text{a}}\) & 3.09 \({}^{\text{a}}\) & 0.25 \({}^{\text{b}}\) & 75.74 \({}^{\text{a}}\) & 0.56 \({}^{\text{a}}\) & 7.75 \({}^{\text{a}}\) & 1.52 \({}^{\text{a}}\) & 0.40 \({}^{\text{a}}\) \\ \cline{1-1}  & 2021 & 5.64 \({}^{\text{a}}\) & 1.09 \({}^{\text{a}}\) & 2.69 \({}^{\text{a}}\) & 0.21 \({}^{\text{b}}\) & 63.00 \({}^{\text{b}}\) & 0.49 \({}^{\text{a}}\) & 6.46 \({}^{\text{b}}\) & 1.22 \({}^{\text{a}}\) & 0.32 \({}^{\text{a}}\) \\ \hline \end{tabular} The same letter after the mean values under each column indicates non-significant differences (\(p>0.05\); Tukey’s), EC: electrical conductivity; TN: total nitrogen; OM: organic matter; Com: compost; NPKCom: chemical fertilizer (NPK) + Composot; NF: unfertilized control.  
\end{table} 
Table 2: The stability of soil chemical properties of NF, NPKCom, and Com treatments from 2018 to 2021.