Field Crop 2025, Vol.8, No.4, 176-186 http://cropscipublisher.com/index.php/fc 181 application maps and receive real-time suggestions based on specific soil, crop types and climatic conditions. These systems are not complex, but the functions behind them can greatly enhance operational efficiency and accuracy (Naresh et al., 2024). 6.3 Role of GIS and variable rate technology (VRT) in optimizing input application The vast field is not a "flat canvas", but rather "fertile soil on one side and a bit poor on the other", and variability is quite common. GIS and VRT were precisely created for this purpose. The GIS system integrates remote sensing, soil sampling and yield data, can demarcate management zones and also output "prescription maps" for VRT equipment to use. The operation mode of VRT is actually very straightforward-it will automatically adjust which plot of land requires more application and which plot can apply less. The use of water, fertilizers and even pesticides has become more targeted. This not only reduces waste but also lowers the environmental impact and helps growers save a considerable amount of input costs (Getahun et al., 2024). This approach is increasingly being used in areas with complex soil conditions or large plot areas, especially for medium and large-sized farms that are willing to invest in equipment and pursue meticulous management (Schimmelpfennig and Lowenberg-Deboer, 2020). 7 Case Study 7.1 Region: Midwest U.S. soybean belt The farmland conditions in the Midwestern United States are complex, and the distribution of soil nutrients is often not very uniform. Some plots have abundant phosphorus and potassium, while others have significantly low levels. In the face of such differences, many local growers have begun to adopt variable fertilization (VRF) to "prescribe the right medicine". This method is based on grid sampling and zonal management, which can customize different amounts of phosphorus (P) and potassium (K) for different areas, thus making the best use of fertilizers where they are most needed. Of course, those who used it early also had concerns, as the increase in production was not always so obvious. However, in recent years, with the advancement of soil data analysis and crop growth monitoring methods, combined with local management approaches, the effect of VRF has become more stable and controllable (Pawase et al., 2023). 7.2 Technology used: integration of NDVI, soil maps, and automated irrigation control Only when the combination of technologies is skillfully applied can management efficiency be truly enhanced. In the central and western regions, some farms have integrated the NDVI vegetation index, soil maps and automatic irrigation systems, achieving "dynamic adjustment and precise response" in field management (Figure 2). The NDVI index is obtained through canopy sensors or drones, which can reflect the growth and nutrient status of soybeans in real time, helping to identify "what needs to be supplemented and what is not lacking". Meanwhile, the soil maps drawn by grid sampling and remote sensing have become the "base map" references for fertilization and irrigation (Miller et al., 2023). Automatic irrigation systems are not used in isolation either. They are usually linked with soil moisture sensors and regulated at fixed points according to the management area. The approach of not overwatering and not randomly spreading fertilizer is precisely the key to supporting the efficient growth of crops (Serrano et al., 2020). 7.3 Outcomes: 12%~18% yield increase, reduced nitrogen runoff, and economic benefits Are these technologies worth piling up together? Judging from the data, the answer is affirmative. In these fields in the Midwestern United States that adopt integrated NDVI, soil maps and automatic irrigation systems, the average yield has increased by 12% to 18%. The reasons are not complicated either: nutrient absorption has improved, input matches crop demands more precisely, and water is utilized more efficiently (Farias et al., 2023). In addition, the problems of nitrogen loss and leaching have also been alleviated. The combination of precise fertilization and precise irrigation has reduced the pressure on the environment and made the ecological account look much better. Let's talk about economic benefits. Although more equipment and technology have been invested, in terms of ultimate returns, as the output and input efficiency improve, profits will naturally increase. It is no wonder that an increasing number of large-scale growers are beginning to proactively embrace these methods.
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