## 4 Discussion
### Synergistic Effect of Anmonia Volatilization Rate Among Concentration, Temperature, and pH  
From the specific fitting equation model selected in Tables 4 and 5, we found that the coefficient of the CIF and IAVFs with temperature and pH was greater than 0.95, which reached a level of significance. This result indicates that the fitting equation is accurate, and also confirms that the temperature-pH superposition of the ammonia volatilization process exists. Coupled with the concentration factor, the quantitative coupling relationship of ammonia volatilization and ammonia concentration, temperature, and pH can be written as follows:  
\[ \begin{split}\text{Y}=(-20.01+7.513\text{pH}+0.3245\text{T}-0.949 6\text{pH}^{2}-0.07564\text{p}\cdot\text{T}-0.002611\text{T}^{2}+\\ 0.0402\text{pH}^{3}+0.00462\text{spH}^{2}\cdot\text{T}+0.000236 \text{pH}\cdot\text{T}^{2}+0.00001387\text{T}^{3}\text{C}+(3.80-\\ 0.7272\text{pH}-0.1661\text{T}+0.02993\text{pH}^{2}+0.02249\text{ pH}\cdot\text{T}+0.0002378\text{T}^{2})\end{split}  \tag{3}\]  
Figure 6: The 3D fitting curve of temperature and pH on the (**a**) CIF and (**b**) IAVFs (SAB). Figure 7: The 3D fitting curve of temperature and pH on the (**a**) CIF and (**b**) IAVFs (SDP). Diammonium phosphate:  
\[ \begin{split}\text{Y}=(-35.71+13.35\text{pH}+0.3913\text{T}-1.676 \text{pH}^{2}-0.08671\text{pH}\cdot\text{T}-0.003744\text{T}^{2}+\\ 0.07017\text{pH}^{3}+0.005198\text{pH}^{2}\cdot\text{T}+0.0002822 \text{pH}\cdot\text{T}^{2}+0.00002617\text{T}^{3})\text{C}+(3.197-\\ 0.6862\text{pH}-0.1311\text{T}+0.03785\text{pH}^{2}+0.01534\text{pH} \cdot\text{T}+0.000647\text{T}^{2})\end{split}  \tag{4}\]  
Using Formulas (3) and (4), we can obtain the ammonia volatilization amount in one hour with different ammonia concentrations, different temperatures, and different pH conditions. In field experiments, we can estimate the ammonia volatilization rate (milligrams per hour) and only need to measure the water temperature, the ammonia concentration, and pH. Now, these parameters can be easily obtained through online monitoring devices. The cumulative ammonia volatilization amount over a period can be calculated by repeated sampling. The Synergistic Effect of Different Ammonium Concentrations, Temperatures, and pH Values on Ammonia Volatilization  
There are many research studies on the soil nitrogen transformation process at home and abroad, which mostly focus on individual factors, but often ignore the joint action between multiple impact factors. Actually, a comprehensive system analysis method should be adopted to study the influence factors of paddy ammonia volatilization because of its interconnectedness and to work on the whole transformation process. Therefore, the establishment of a mathematical model for a single factor is not enough, and a coupling mathematical model for a variety of key influence factors is necessary in quantitative research on ammonia volatilization in an actual ecological environment. According to combination research on the affecting factors of ammonia volatilization, a valuable and guiding index of adjusting crop growth and reasonable fertilization can be obtained. The particle size, organic matter content, and cation exchange capacity (CEC) of soil affect its adsorption of NH\({}_{4}\)+, and a smaller clay particle size and higher organic matter content lead to a stronger ability of the soil to adsorb ammonium ions, which is more conducive to reducing ammonia volatilization. [PERSON] [31] found that the amount of ammonia volatilization showed a positive correlation with soil pH and a negative correlation with CEC. Soil clay mineral types, fertilization and cultivation methods [32], and even microbial activity in the soil can affect the process of ammonia volatilization [23].