## 5 Conclusions  
In this paper, we constructed a mathematical model of temperature, pH, and ammonia nitrogen concentration with ammonia volatilization. The results show that the ammonia volatilization characteristics of different kinds of nitrogen fertilizer are divergent: ammonium bicarbonate more easily releases ammonia than diammonium phosphate. In this research, we found that the ammonia nitrogen concentration, temperature, and pH had obvious positive effects on ammonia volatilization; a fitting relation of ammonia volatilization treated with ammonium bicarbonate and diammonium phosphate with concentration, temperature, and pH was obtained.  
1. Under the same pH conditions, both SAB and SDP exhibited an excellent positive correlation between the ammonia volatilization amount and ammonium nitrogen concentration. At different temperatures, for SAB, the CIF of the fitting equation between temperature and the amount of ammonia volatilization was between 0.0030 and 0.2434, and the \(R^{2}\) of the fitting equation was between 0.9214 and 0.9897. The coefficient CIF of SDP was between 0.0012 and 0.2103, and the \(R^{2}\) of the fitting equation was between 0.8932 and 0.9904.  
2. The CIF and IAVFs are linearly correlated with temperature. As pH increases, temperature has an increasing effect on the CIF, with slopes of 0.0005 to 0.0105 (SAB) and 0.0004 to 0.0105 (SDP). The slopes of the IAVFs fitting equation for temperature are 0.0053 to 0.0397 (SAB) and 0.0055 to 0.0274 (SDP).  
3. There is a quadratic correlation between the CIF and pH with \(\varepsilon>0\), which leads to a rapid increase in CIF with increasing pH. This is because pH is the negative logarithm of the concentration of H\({}^{+}\) in the solution, so there is no linear correlation between the pH value and the H\({}^{+}\) concentration. The IAVFs are linearly correlated with pH, and the slopes of the IAVFs fitting equation for pH are 0.0744 to 0.3814 (SAB) and 0.1366 to 0.3721 (SDP).  
4. Considering that temperature and pH are linearly and quadratically correlated with the CIF, respectively, and that temperature and pH are linearly correlated with the IAVFs, a binary cubic model was used to fit the relationship between temperature and pH to the CIF and IAVFs. The simulation results show that the correlation coefficients between the CIF and IAVFs for SAB are 0.9980 and 0.9680, and the correlation coefficients are 0.9946 29 and 0.9708 for SDP.  
Conceptualization, J.X. and A.D.; methodology, J.X.; software, J.X.; validation, Y.C., T.Y. and J.L.; formal analysis, J.X.; investigation, J.X. and C.X.; resources, A.D.; data curation, Y.C. and T.Y.; writing--original draft preparation, J.X. and Y.C.; writing--review and editing, A.D.; supervision, J.X.; project administration, A.D.; funding acquisition, C.X. and A.D. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China, funding number: 22166019.  
Not applicable.  
Data Availability Statement: Data are contained within the article.  
**Acknowledgments:** The authors thank Lvheng Technology Co. Ltd. (Nanchang) for providing convenient reagent purchase and experimental customization.  
**Conflicts of Interest:** The authors declare no conflicts of interest. The funders had no role in the design of the study, in the collection, analyses, or interpretation of data, in the writing of the manuscript, or in the decision to publish the results.