## 3 Proposed Methods  
### Soil Sample Collection  
Soil samples were collected in Xinjiang Autonomous Region of China, as shown in Figure 1. The collection sites are located in three experimental fields in Tumushuke, Shihezi, and Tacheng in Xinjiang, China, which are all operated and managed by Shihezi University. The longitude and latitude of the Tumushuke region range from 40\({}^{\circ}\)04\({}^{\prime}\) to 39\({}^{\circ}\)36\({}^{\prime}\) N and 78\({}^{\circ}\)38\({}^{\prime}\) to 79\({}^{\circ}\)50\({}^{\prime}\) E. The annual average temperature is 11.6 \({}^{\circ}\)C, the average temperature in the hottest month (July) is 25.0 \({}^{\circ}\)C\(-\)26.7 \({}^{\circ}\)C, the average temperature in the coldest month (January) is \(-\)6.6 \({}^{\circ}\)C\(-\)7.3 \({}^{\circ}\)C, the annual average frost-free period is about 225 days, the annual precipitation is 38.3 mm, and the altitude is 425-437 m.  
The longitude and latitude of Shihezi region range from 44\({}^{\circ}\)25\({}^{\prime}\) to 44\({}^{\circ}\)27\({}^{\prime}\) N and 85\({}^{\circ}\)40\({}^{\prime}\) to 86\({}^{\circ}\)10\({}^{\prime}\) E, respectively. The annual average temperature is 9.2 \({}^{\circ}\)C, the average temperature in the hottest month (July) is 25.1-26.1 \({}^{\circ}\)C, the average temperature in the coldest month (January) is \(-\)20.6 \({}^{\circ}\)C\(-\)7.3 \({}^{\circ}\)C, the annual average frost-free period is about 170 days, the annual precipitation is 43.5 mm, and the altitude is 510-520 m.  
The longitude and latitude of Tacheng region range from 46\({}^{\circ}\)31 to 46\({}^{\circ}\)37\({}^{\prime}\) N and 83\({}^{\circ}\)37\({}^{\prime}\) to 83\({}^{\circ}\)41\({}^{\prime}\) E, respectively. The annual average temperature is 7.6 \({}^{\circ}\)C, the average temperature in the hottest month (July) is 24.5 \({}^{\circ}\)C to 25.8 \({}^{\circ}\)C, the average temperature in the coldest month (January) is \(-\)26.6 \({}^{\circ}\)C to \(-\)9.6 \({}^{\circ}\)C, the annual average frost-free period is about 155 days, the annual precipitation is 27.1 mm, and the altitude is 1100 m to 1150 m. The cash crops are cotton and wheat, and the soil properties are loamy and silt clay. Tumushuke, Shihezi, and Tacheng test fields were established with ten 5 km grids as sampling units. To make each sampling point representative of the soil properties of the sampling unit, 80 soil organic matters were sampled for each sampling, and a total of 800 soil samples were collected. Five meters at each sampling point according to the five-point sampling method \(\times\) samples were collected within 5 m. A total of five soil samples were collected at each sampling point. The samples were fully mixed and loaded into sampling bags. To avoid lead pollution with different contents caused by human activities, the sampling distance from the highway was at least 150 m during the sampling process. Figure 1: Data collection location of soil organic matter hyperspectral database. Considering that soil macro-nutrients are concentrated on the earth's surface, soil samples were collected at a depth of about 15 cm according to traditional soil sampling technology. The plant tissue, gravel, and other impurities were removed from the sample. The sample was ground and screened after air drying so that the particle size of the soil was less than 0.25 mm. The sample was divided into two parts; one was for determining the content of soil elements, and the other was for the indoor hyperspectral. The potassium dichromate volumetric method was used to determine the content of S, and the delta professional 4050 portable X-ray fluorescence spectrometer (Olympus, Allen Town, Pennsylvania, USA) was used to measure the content of soil phosphorus and potassium. The equipment was equipped with an Au target micro X-ray excitation source, and a Peltier semiconductor cooled SDD detector was used. The detector area was 25 mm\({}^{2}\), and the energy resolution was 128 ev. The detector can simultaneously measure 38 elements, including soil phosphorus and potassium.