## 7 Potential Research Directions and Thoughts
The effects of irrigating with brackish water or alternating between freshwater and brackish water for three to four consecutive years on cotton growth characteristics and yield have been observed. Solar-induced chlorophyll fluorescence (SIF), as a direct measure of vegetative photosynthesis, has emerged as an effective indicator for estimating late-season crop yield. These correlation results offer new insights for the assessment of profile salinity [161; 162; 133]. Vegetation indices derived from satellite data serve as a major source for cost-effective, long-term estimates of crop aboveground biomass. For instance, utilizing biomass-related datasets generated from 1990 to 2024 will enhance our understanding of the fundamental impacts of deep-profile salinity on long-term crop yield perturbations. Australia's vision plan for digital mapping research explicitly states [163] that new digital mapping products should offer solutions tailored for farms. Each farm is likely to require specific management practices. This study leverages data collected locally from farmers, agronomists, and agricultural machinery to develop farm-specific, farm-level digital agricultural maps. The U.S. Department of Agriculture's Natural Resources Conservation Service (USDA-NRCS) Soils2026 program aims to provide fundamental thematic maps of soils and ecological zones that are beneficial for land managers, ecologists, modelers, and other natural resource professionals [164]. This initiative will depend on advanced digital soil mapping technologies, which will also be equally applicable to on-farm salinity management needs. Satellite-borne, airborne, and near-ground platform data each have their own advantages and disadvantages; the surface information obtained from a single system is often incomplete. Therefore, the potential of satellite-ground sensing data should be fully leveraged, and the strengths of each platform should be integrated to enable multi-scale collaborative monitoring of soil salinization [20; 165; 28]. Future research could synchronize observations from satellite-to-aircraft, satellite-to-ground, aircraft-to-ground, or satellite-to-aircraft-to-ground based on satellite transit or UAV flight operation times, ensuring that data from multiple platforms can mutually validate each other and that observations from various sensors can enhance overall understanding [166; 115]. Building on clear ground truth and sufficient prior knowledge, the scale assessment of the three dimensions-- \"observation data-method-accuracy\"--should be conducted by integrating the spatial scale transformation method with a well-defined geological mechanism and collaborative observational information [166]. Furthermore, by utilizing soil moisture or organic matter as a linkage, it is essential to further investigate the optical mechanisms connecting spectral information and soil salinity and subsequently establish a radiation transfer model tailored for soil salinity. Additionally, models such as SWAP(Soil-Water-Atmosphere-Plant) [167] or HYDRUS [168] with robust physical mechanisms can be driven by multi-source satellite-to-ground sensor data to elucidate the processes of soil water and salt transport from a more microscopic perspective, ultimately establishing a novel paradigm for remote sensing inversion of soil salinity characterized by a strong physical foundation and generalization capabilities, thereby further minimizing the likelihood of error propagation across different scales.