## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Group** & **CK** & **ZY1** & **ZY2** & **ZY3** & **ZY4** \\ \hline Al-P (mg kg\({}^{-1}\)) & 1 d & 56.537 \(\pm\) 4.46 & 62.335 \(\pm\) 2.62 & 75.459 \(\pm\) 3.26 & 81.821 \(\pm\) 8.53 & 89.518 \(\pm\) 26.14 \\  & 30 d & 46.542 \(\pm\) 2.40 & 52.215 \(\pm\) 6.31 & 50.742 \(\pm\) 4.92 & 53.207 \(\pm\) 9.30 & 63.871 \(\pm\) 10.25 \\ \hline Fe-P (mg kg\({}^{-1}\)) & 1 d & 252.061 \(\pm\) 9.11 & 273.120 \(\pm\) 4.50 & 269.544 \(\pm\) 8.02 & 282.675 \(\pm\) 5.08 & 309.402 \(\pm\) 9.85 \\  & 30 d & 187.870 \(\pm\) 8.14 & 197.948 \(\pm\) 12.34 & 213.640 \(\pm\) 14.37 & 223.829 \(\pm\) 5.78 & 242.288 \(\pm\) 7.42 \\ \hline O-P (mg kg\({}^{-1}\)) & 1 d & 193.853 \(\pm\) 6.58 & 197.207 \(\pm\) 14.17 & 209.614 \(\pm\) 10.68 & 208.502 \(\pm\) 23.62 & 190.175 \(\pm\) 17.28 \\  & 30 d & 225.881 \(\pm\) 20.38 & 223.786 \(\pm\) 8.87 & 227.749 \(\pm\) 51.47 & 215.778 \(\pm\) 15.96 & 224.666 \(\pm\) 6.99 \\ \hline Ca-P (mg kg\({}^{-1}\)) & 1 d & 80.026 \(\pm\) 21.17 & 65.676 \(\pm\) 9.60 & 78.419 \(\pm\) 12.69 & 69.958 \(\pm\) 16.27 & 68.529 \(\pm\) 5.50 \\  & 30 d & 68.581 \(\pm\) 2.91 & 65.176 \(\pm\) 5.20 & 81.834 \(\pm\) 13.46 & 80.979 \(\pm\) 26.19 & 88.246 \(\pm\) 4.84 \\ \hline Org-P (mg kg\({}^{-1}\)) & 1 d & 189.316 \(\pm\) 6.29 & 134.531 \(\pm\) 43.24 & 157.089 \(\pm\) 49.55 & 197.565 \(\pm\) 13.71 & 162.338 \(\pm\) 31.40 \\  & 30 d & 19.655 \(\pm\) 15.17 & 27.51 \(\pm\) 1.18 & 6.52 \(\pm\) 0.00 & 47.57 \(\pm\) 32.67 & 17.89 \(\pm\) 23.97 \\ \hline TP (mg kg\({}^{-1}\)) & 1 d & 782.297 \(\pm\) 38.56 & 732.688 \(\pm\) 49.40 & 790.124 \(\pm\) 42.53 & 840.520 \(\pm\) 47.13 & 819.962 \(\pm\) 35.72 \\  & 30 d & 541.977 \(\pm\) 34.80 & 557.467 \(\pm\) 13.57 & 576.137 \(\pm\) 58.03 & 605.509 \(\pm\) 35.48 & 630.992 \(\pm\) 6.04 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Phosphorus forms and contents in soil after 1 d and 30 d of simulated incubation. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Treatments** & **CK** & **ZY1** & **ZY2** & **ZY3** & **ZY4** \\ \hline pH (H\({}_{2}\)O) & 5.81 \(\pm\) 0.10 a & 4.92 \(\pm\) 0.07 b & 4.53 \(\pm\) 0.03 d & 4.75 \(\pm\) 0.01 c & 4.36 \(\pm\) 0.01 e \\ TN (g kg\({}^{-1}\)) & 1.38 \(\pm\) 0.05 a & 1.39 \(\pm\) 0.05 a & 1.13 \(\pm\) 0.01 b & 1.13 \(\pm\) 0.01 b & 1.40 \(\pm\) 0.03 a \\ TP (g kg\({}^{-1}\)) & 0.61 \(\pm\) 0.01 b & 0.68 \(\pm\) 0.01 a & 0.56 \(\pm\) 0.01 c & 0.55 \(\pm\) 0.01 c & 0.70 \(\pm\) 0.02 a \\ TK (g kg\({}^{-1}\)) & 14.60 \(\pm\) 0.15 b & 15.24 \(\pm\) 0.28 a & 14.07 \(\pm\) 0.17 c & 14.41 \(\pm\) 0.06 b & 15.00 \(\pm\) 0.06 a \\ SOM (g kg\({}^{-1}\)) & 27.97 \(\pm\) 3.16 a & 257.77 \(\pm\) 2.21 b & 18.83 \(\pm\) 1.08 e & 23.70 \(\pm\) 1.90 d & 24.17 \(\pm\) 0.55 c \\ Olsen-P (mg kg\({}^{-1}\)) & 27.38 \(\pm\) 3.26 b & 15.54 \(\pm\) 0.48 c & 23.27 \(\pm\) 0.42 b & 16.78 \(\pm\) 1.05 c & 52.24 \(\pm\) 0.64 a \\ Al-P (mg kg\({}^{-1}\)) & 197.594 & 160.844 & 143.067 & 213.511 & 247.060 \\ Fe-P (mg kg\({}^{-1}\)) & 394.128 & 331.770 & 321.152 & 362.866 & 335.477 \\ Ca-P (mg kg\({}^{-1}\)) & 110.903 & 41.510 & 24.898 & 25.237 & 157.61 \\ Org-P (mg kg\({}^{-1}\)) & 103.778 & 42.106 & 90.512 & 115.099 & 151.972 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Physicochemical indicators of soil in each treatment group (a, b, c, d, e indicate significant differences (\(p<\) 0.05) by Duncan’s test). the increase in the total phosphorus content in the soil during the harvest period of CO did not show a significant difference. Overall, the application of biogas slurry not only directly supplies a readily available phosphorus source but also increases the proportions of metal ion-bound phosphorus, such as Fe-P, Al-P, and Ca-P, which are relatively easy for plants to absorb and utilize.