# Assessing the Long-Term Evolution of Abandoned Salinized Farmland via Temporal Remote Sensing Data
## 6 Conclusions  
In arid and semiarid water-logged areas, abandoned salinized farmland plays an essential role in acting as an evaporation sink gathering salt from the surrounding cropping area. However, traditional methods for land-use (land cover) classification fail to detect these wastelands. This study introduced a robust approach to detect abandoned saline land in the Htetao Irrigation District using 32-year time-series remotely sensed data. The proposed method is based on the idea of \"elimination\" to detect abandoned saline land step by step, which provides inspiration for monitoring the planting pattern of specific crops, or progress such as desertification or urbanization. At the same time, the dynamics of the cropping structure were monitored. The combination of the \(K\)-means cluster algorithm and the shape-model-fitting method successfully identified the specific crop, where the estimates agreed well with the statistics. The results show that the cropland in Hteao has continuously expanded during the last thirty years. An increasing number of farmers in Hteao have tended to plant high stem crops (maize and sunflower) instead of spring wheat from 1988 to 2019. The salinization degree was evaluated by the SI using an established exponential relationship between the SI and measured soil EC. The saline situation has been mitigated during recent decades, indicating that water-saving techniques, drainage facilities, and optimized cropping structures represent desalinization progress. Thermal information and the SI were used to distinguish the abandoned salinized farmland from other non-vegetative lands. The detected area of abandoned salinized farmland has continuously decreased, while many small wastelands have vanished in eastern and western Hteao. However, in central Hteao, a group of large-area abandoned salinized farmland has existed for 30 years. The strong effect of the dry drainage system has slowed the reutilization progress in these wastelands. However, a decrease in the groundwater table and salt-tolerant plants have created an opportunity to launch a saline field improvement project to reutilize the abandoned salinized farmland where the dry drainage system has already collapsed.  
The following are available online at [[https://www.mdpi.com/article/10.3390/rs13204057/s1](https://www.mdpi.com/article/10.3390/rs13204057/s1)]([https://www.mdpi.com/article/10.3390/rs13204057/s1](https://www.mdpi.com/article/10.3390/rs13204057/s1)), Table S1: Acquisition Time and Identifiers of Used Satellite Data.  
[PERSON] performed data collection and processing; [PERSON] and [PERSON] analyzed the data and interpreted the results; [PERSON] and [PERSON] supported the writing, review and editing; [PERSON] and [PERSON] provided the suggestions and reviews. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Science Foundation of China (Grant No. 51790532).  
**Acknowledgments:** We are grateful to the editor and anonymous reviewers for their valuable comments and others who contributed to this paper.  
**Conflicts of Interest:** The authors declare no conflict of interest.