## 3 Results and Analysis
### Salinity Monitoring  
The RS salinity monitoring index models S1 DI1, S1 DI2, S1 DI3, and SIDI4 were calculated using the formulas in Table 1, and the Jenk natural discontinuity point classification method was used to divide the value range of the above model into three saline soil grades [16] (Table 3). The soil salimization distributions of the four monitoring models were obtained, as illustrated in Figure 4.  
It can be seen in Figure 4 that the soil salinity in the cotton fields in the Alar reclamation area retrieved by the S1 DI1, S1 DI2, S1 DI3, and S1 DI4 models is mainly non-saline soil, while the distribution of light saline soil and moderately saline soil is slightly different. For the S1 DI1-derived results, the light saline soil is mainly distributed in the southeast area of the 9 th regiment and the area along the Tarim River in the 12 th regiment of the reclamation area. The moderate saline soil is scattered in the Alar reclamation area based on the SIDI1 model. Among them, the central region of the 9 th Regiment and the northwest region of the 10 th Regiment are the most numerous and widely distributed. For the SIDI2-derived result, the light saline soil is mainly distributed in the middle and northwest of the 9 th regiment and the area along the Tarim River in the 12 th regiment of the reclamation  
Figure 4: The spatial distribution of soil salimization levels of the cotton field in the Alar reclamation area of four models.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Model** & **Non-Saline Soil** & **Mildly Saline Soil** & **Moderately Saline Soil** \\ \hline S1 DI1 & \textless{}0.8770 & 0.8770–1.0486 & 1.0486–1.13918 \\ S1 DI2 & \textless{}0.5935 & 0.5935–0.7171 & 0.7171–0.9643 \\ S1 DI3 & \textless{}0.5692 & 0.5692–0.7176 & 0.7176–1.0144 \\ S1 DI4 & \textless{}0.6586 & 0.6586–0.8036 & 0.8036–1.0936 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Soil Salimization Classification of Cotton Fields in the Alar Reclamation Area.  
area; the moderate saline soil is scattered in the Alar reclamation area. Moreover, based on the SIDI3-derived result, it can be found that the light saline soil is mainly distributed in the central area of the 9 th regiment and the northeast area of the 12 th regiment in the reclamation area; the moderate saline soil is scattered in the Alar reclamation area. The central part of the 9 th regiment and the 12 th regiment are the most widely distributed and the largest in the Taklamakan Desert. For the S1 DI4-derived results, the light saline soil is mainly distributed in the central area of the 9 th regiment and the area along the Tarim River in the 12 th regiment of the reclamation area; the moderate saline soil is scattered in the Alar reclamation area. Among them, the central region of the 9 th and 10 th regiments and the 12 th regiments are the most widely distributed in the Taklamakan Desert. The inversion results of the four models for the non-salinized cotton soil in the Alar reclamation area are roughly the same, but there are some differences in the inversion results for the mildly saline soil and the moderately saline soil. As a result, it is necessary to select a suitable and proper salinity monitoring index model with a higher inversion accuracy and remote sensing images.