## 3 Results
### Ammonia Loss Incubation Study  
The daily loss of NH\({}_{3}\) from urea fertilizer during the period of the incubation study over 28 days is shown in Figure 3. There was no activity of NH\({}_{3}\) volatilization in T0. Meanwhile, in (soil with urea only) T1, NH\({}_{3}\) loss started on the second day after the application of urea. The NH\({}_{3}\) volatilization started on third day in T6 and T7 (commercial biochar potting media). The loss sped up and peaked on fifth, eighth, and ninth days in T1, T6, and T7, respectively. The NH\({}_{3}\) loss in T1, T6, and T7 started early, and similarly it ceased to 1% of added N early in the soil compared to the treatments amended with RSRH biochars (T2, T3, T4, and T5). In T2 and T3, the NH\({}_{3}\) loss was delayed by up to 7 days while the loss of NH\({}_{3}\) in T4 and T5 was delayed by up to 6 days. In T2 and T3, the loss peaked up on the fourteenth and fifteenth days, respectively; meanwhile, in T4 and T5, the loss peaked up on the twelfth day. The trend of the graph shows that the loss of NH\({}_{3}\) peaked up and reduced gradually up to twenty-ninth day, until added urea ceased up to 1%. The treatments with biochar as an additive (T2, T3, T4, and T5) significantly minimized NH\({}_{3}\) loss compared to urea without additives (T1) and commercial biochar potting media (T6 and T7) (Table 5). Treatment T3 was more distinct in minimizing NH\({}_{3}\) loss, which was about 41% followed by T2, T4, and T5 at 33%, 30%, and 27%, respectively, over T1. Further,  
\begin{table}
\begin{tabular}{l c c c c} \hline \hline \multicolumn{1}{c}{**Property**} & \multicolumn{1}{c}{**Rice Straw**} & \multicolumn{1}{c}{**Rice Husk**} & \multicolumn{1}{c}{\
\begin{tabular}{c} **Rice Straw** \\ **Biochar** \\ \end{tabular} } & \multicolumn{1}{c}{
\begin{tabular}{c} **Rice Husk** \\ **Biochar** \\ \end{tabular} } \\ \hline pH (water) & 7.0 & 6.5 & 9.2 & 9.1 \\ CEC (cmol kg\({}^{-1}\)) & 38.0 & 34.5 & 75.6 & 66.6 \\ Total nitrogen (\%) & 0.38 & 0.25 & 0.45 & 0.33 \\ Available P (mg kg\({}^{-1}\)) & 10.7 & 9.8 & 14.3 & 14.3 \\ Exchangeable Ca (mg kg\({}^{-1}\)) & 3205 & 320 & 3599 & 1048 \\ Exchangeable Mg (mg kg\({}^{-1}\)) & 1288 & 2186 & 809 & 508 \\ Exchangeable K (mg kg\({}^{-1}\)) & 25,450 & 1945 & 12,030 & 4925 \\ Exchangeable Na (mg kg\({}^{-1}\)) & 52.1 & 59.3 & 246.3 & 256 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Selected physico-chemical properties of rice straw, rice husk, rice straw biochar, and rice husk biochar.  
Figure 2: Rice straw biochar surface at 1000\(\times\) magnification under SEM.  
the pH of soil amended with RSRH biochars was significantly higher than that of T0, T1, T6, and T7.  
Additionally, biochar successfully adsorbed nutrients from the soil. T2, T3, and T4 showed a significant NH4+ retention in soil (Table 5) by retaining the highest amount of NH4+ by 95% and 79%, respectively, over T1, followed by T4 and T5, which were 54% and 12%, respectively. Further, the NO3- ions in the soil were found to be higher in T2 and T3. Commercial biochar potting media T6 and T7 did not show any significant increment in retention of NH4+ and NO3- in comparison to treatments amended with RSRH biochars.