**2. Materials and Methods**

#### *2.1. Study Area*

The study area is located in oasis agricultural areas in Bayingolin Mongol Autonomous Prefecture, Xinjiang Uyghur Autonomous Region, China, encompassing the area 40.61◦–42.44◦ N, 85.82◦–87.14◦ E (Figure 1). This area is situated in the southern foothills of the Tianshan Mountains, on the north-eastern edge of the Tarim Basin, adjacent to the west bank of Bosten Lake, and to the north of the Taklimakan Desert. This region features a warm temperate continental climate, with much more evaporation than precipitation. It has a representative planting pattern in the arid and semi-arid regions of Northwest China.

The major crop types cultivated from spring to autumn include cotton, spring corn, summer corn, pear, chili pepper, tomato, etc. Cotton is sown from early April to early May and harvested by the end of September. Spring corn is sown in mid-April to early June and harvested in mid-August to mid-September. Summer corn is sown in mid-June to mid-July and harvested by early October. Pear starts budding in late March, flowering from late March to the end of April, fruiting from May to early September, and is harvested in September. Chili pepper and tomato seedlings are nurtured in greenhouses from February to March, transplanted to open fields from mid-April to early May. Tomato

is harvested in August, and chili pepper is harvested in October. Phenological calendars of the five crop types are summarized in Table 1.

**Figure 1.** The study area across Yuli, Korla, Bohu, Yanqi, Hejing, and Hoxud counties in Bayin Guoyu Mongolian Autonomous Prefecture, Xinjiang Uygur Autonomous Region, China. The in-situ collected sample points of major crop types are highlighted. The overlapped area of Sentinel-1 IW2 sub-swath (in the blue rectangle) and mosaicked coverage of Sentinel-2 scenes (in the black rectangle) is the area of interest in this study. The background image is a true color Google Earth high-resolution image. Map data: Google Earth, Image © 2020 Europa Technologies.

**Table 1.** Phenological calendars of the major crop types in the study site.


Legend: Sowing; ד Budding; ♠ seedling nurturing; -Transplanting; <sup>յ</sup> Growing; <sup>√</sup> Harvesting.
