## 3 Results
### Nitrogen Adsorption Isotherms  
The experimental data on Langmuir N adsorption isotherms 1, 2, and 3 showed negative slopes or intercepts (Table 11). This suggests that N adsorption in this present study does not follow Langmuir approach [30]. \begin{table}
\begin{tabular}{l c c c c} \hline \hline \multirow{2}{*}{**Treatment**} & \multicolumn{4}{c}{**Adsorbed K (\(\mu\)g g\({}^{-1}\)) q\({}_{e}\)**} \\ \cline{2-5}  & **500** & **1000** & **2000** & **3000** & **4000** \\ \cline{2-5}  & & & **Added K (\(\mu\)g)** & \\ \hline Soil & 85.53 E bc & 181.20 D b & 947.20 A c & 350.53 C c & 411.20 B c \\ CLB & 59.97 C c & 336.63 C a & 1196.63 A a & 843.30 B a & 1019.97 AB a \\ B1 & 115.83 E b & 180.83 D b & 1004.83 A bc & 514.83 C bc & 655.50 B b \\ B2 & 231.83 E a & 270.50 D ab & 1067.17 A b & 586.17 C b & 752.83 B b \\ B3 & 107.03 E bc & 271.70 D ab & 1013.70 A bc & 527.70 C bc & 701.03 B b \\ \hline \hline \end{tabular} Note: Treatment and added K rate interaction was significant at F probability level of \(<\)0.0001. Different capital letters in a row and different small letters in a column are significantly difference between means using Tukey’s test at P \(\leq\) 0.05.  
\end{table} 
Table 10: Potassium addition to potassium adsorption based on different treatments. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multirow{2}{*}{**Treatment**} & \multicolumn{4}{c}{**Adsorbed N (\(\mu\)g g\({}^{-1}\)) q\({}_{e}\)**} \\ \cline{2-5}  & **500** & **1000** & **2000** & **3000** & **4000** \\ \cline{2-5}  & \multicolumn{4}{c}{**Added N (\(\mu\)g)**} \\ \hline Soil & 112.39 E c & 276.15 D d & 491.59 C d & 833.12 B d & 1291.40 A c \\ CLB & 327.17 E a & 574.99 D a & 1112.66 C a & 1636.32 B a & 2244.04 A a \\ B1 & 187.08 E b & 378.86 D c & 683.03 C c & 945.17 B c & 1141.93 A d \\ B2 & 201.14 E b & 336.88 D c & 701.76 C c & 931.21 B c & 1398.83 A b \\ B3 & 210.48 E b & 458.30 D b & 776.48 C b & 1075.98 B a & 1361.47 A b \\ \hline \hline \end{tabular} Note: Treatment and added N rate interaction was significant at F probability level of \(<\)0.0001. Different capital letters in a row and different small letters in a column are significantly difference between means using Tukey’s test at P \(\leq\) 0.05.  
\end{table} 
Table 8: Nitrogen addition to nitrogen adsorption based on different treatments. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multirow{2}{*}{**Treatment**} & \multicolumn{4}{c}{**Adsorbed P (\(\mu\)g g\({}^{-1}\)) q\({}_{e}\)**} \\ \cline{2-5}  & **625** & **1250** & **2500** & **3750** & **5000** \\ \cline{2-5}  & \multicolumn{4}{c}{**Added P (\(\mu\)g)**} \\ \hline Soil & 416.31 C a & 562.00 B a & 675.52 B b & 798.68 A b & 833.56 A b \\ CLB & 167.58 D d & 531.13 C a & 1120.71 B a & 1744.46 A a & 1593.63 A a \\ B1 & 258.40 C b & 360.14 BC b & 453.18 AB c & 559.69 A c & 534.69 A c \\ B2 & 222.61 C c & 305.87 C c & 424.99 B c & 469.52 AB c & 553.37 A c \\ B3 & 201.83 D c & 305.59 C c & 398.40 B c & 505.17 A c & 499.44 A c \\ \hline \hline \end{tabular} Note: Treatment and added P rate interaction was significant at F probability level of \(<\)0.0001 and added P rate interaction was not significant at P = 0.05. Different capital letters in a row and different small letters in a column are significantly difference between means using [PERSON]’s test at P \(\leq\) 0.05.  
\end{table} 
Table 9: Phosphorus addition to phosphorus adsorption based on different treatments. Nitrogen adsorption followed Freundlich approach because of significant coefficient of determination (R\({}^{2}\)) and lower \(\chi^{2}\) values compared with Langmuir (type 4) and Temkin adsorption equations (Table 12).