## 2 Materials and Methods  
This study conducted simultaneous field wheat fertilizer control trials at two locations: Xinhua Agricultural Cooperative Farm, Linhe district, and Yonglian village, Xin-guangzhong town, Wuyuan county Bayannur city, Inner Mongolia Autonomous Region in 2019 and 2020. The locations of the experimental plots are shown in Figure 1.  
The test variety was the locally dominant wheat variety, Yongliang 4. Sowing took place in early March 2019 and 2020, and harvesting took place in late July 2019 and 2020. The seeding rate was 375 kg/hm\({}^{2}\), using a wheat planter for seed fertilizer layer seeding with a row spacing of 15 cm. Nitrogen, phosphorus, and potash fertilizers were applied together as the seed fertilizer at the time of sowing, followed by an additional treatment during the jointing stage (3) of the wheat. Irrigation was carried out in a water-saving mode, twice during the whole lifecycle (jointing (3) + flowering (6), each irrigation 900 m\({}^{3}\)/hm\({}^{2}\)). Other management measures were in line with conventional wheat cultivation practices. The fertilization experiment included six different modes: CK, farmer model (FM), control of fertilization patterns (CF), control of fertilization-N (CF-N0), control of fertilization-P (CF-P0), and control of fertilization-K (CF-K0). Details of the specific fertilization rates and methods are shown in Table 1.  
Digital image data were collected in late May (tasseling stage (5)), mid-June (filling stage (7)), and early July (maturity stage (8)) in 2019. A DJI Royal MAVIC 2 Professional Edition (Manufactured by DJI Innovations (Shenzhen, China) Co., Ltd., DJI unmanned aerial vehicles (UAVs) are produced at the DJI UAV production base in Chengdu, China. All lenses were purchased from the same company.) equipped with a Hasselblad L1D-20c camera was used for high-definition digital photography. The camera features a new 1-inch 20-megapixel CMOS sensor, a built-in wide-angle lens with a 28 mm equivalent focal length, an adjustable aperture value ranging from f/2.8 to f/11, and a maximum sensitivity of 12,800. The study collected and stored digital images in the TIF format. The drone's flight lasted approximately 30 min. To minimize the impact of external factors on image acquisition, the study was conducted between 10:00 and 14:00 under clear and cloudless sky conditions. Radiometric correction was carried out using a black-and-white board to minimize errors, and the UAV was flown at an altitude of 50 m.  
Digital image indices have been effectively used to estimate plant physiological and biochemical parameters, such as leaf area index, biomass, and nitrogen content. This \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Treatments**} & \multicolumn{4}{c}{**Fertillizer Rate (kg/hm2)**} \\ \cline{2-5}  & \multicolumn{2}{c}{**Nitrogen**} & \multicolumn{2}{c}{**Phosphate Fertillizer**} & **Potash Fertillizer** \\ \cline{2-5}  & **Sowing N** & **Top-Dressing N** & **(P2\({}_{\text{O}}\)s)** & **(K2\({}_{\text{O}}\))** \\ \hline CK & 0 & 0 & 0 & 0 \\ FM & 94.5 & 207 & 241.5 & 0 \\ CF & 52.5 & 124.5 & 61.5 & 60 \\ CF-N0 & 0.0 & 0.0 & 61.5 & 60 \\ CF-P0 & 52.5 & 124.5 & 0.0 & 60 \\ CF-K0 & 52.5 & 124.5 & 61.5 & 0.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: This table displays the fertilization rates of treatments. Figure 1: Map of test site locations. effectiveness was due to their ability to enhance vegetation information, reduce the impact of non-vegetation elements on plant mapping features, and improve the accuracy of remote sensing inversion. This study screened digital image indices for monitoring wheat growth research, integrating insights from previous studies with a pre-analysis of experimental data.