## 4 Discussion  
### Validity of Satellite-Derived Soil Moisture  
The comparison of field-measured soil moisture data and satellite-derived estimates confirmed the effectiveness of remote sensing technologies in monitoring soil water dynamics in avocado orchards. The strongest correlations between field measurements and satellite data were consistently observed at the 30 cm depth, corresponding to the root zone dynamics of avocado trees. This depth is critical as it represents the upper portion of the root zone, where most water uptake occurs, especially during irrigation and evaporation processes. Performance of 30 cm Depth Sensors  
The 30 cm depth demonstrated the strongest correlation with satellite-derived soil moisture data, with a correlation coefficient of 0.8237 in 2021. This depth reflects the most dynamic zone of soil moisture variation due to its proximity to the root zone, which is most sensitive to changes in irrigation and rainfall [43]. Root uptake is most active in this zone, playing a significant role in determining the immediate water availability for plants [44]. This dynamic behavior of the 30 cm depth likely explains its strong correlation with the satellite data, as it captures the surface-level water availability most influenced by seasonal changes, irrigation practices, and evaporation processes. The high performance at this depth is also consistent with the findings in other agricultural studies that indicated that shallow soil layers are more responsive to short-term changes in environmental conditions [28], such as precipitation and irrigation, which remote sensing technologies can detect. For instance, similar results were observed in studies of vineyards and other high-water-demand crops, where satellite-derived soil moisture values showed strong correlations with field measurements at depths ranging from 30 cm to 60 cm [45; 46]. These studies support the relevance of a 30 cm depth for effective satellite-based soil moisture monitoring, especially in the context of surface-level water availability. Temporal and Spatial Accuracy  
The ERA5-derived soil moisture estimates effectively captured soil moisture dynamics during the wet and dry seasons, as also shown in other studies [47; 48]. These satellite-derived soil moisture estimates closely tracked fluctuations in field-based measurements, especially following precipitation events. This temporal alignment demonstrates that ERA5 data are sensitive to seasonal transitions, providing valuable insights into the water availability and irrigation needs of avocado orchards [49; 50]. However, while ERA5 data effectively capture general trends in soil moisture, their spatial resolution limits their ability to capture fine-scale variability within an orchard, particularly in areas with heterogeneous soil textures or microclimates [51]. Previous studies have also pointed out that higher-resolution satellite data or additional ground-based measurements might be needed to refine soil moisture estimates at the field level. For instance, in a prior study [52], the authors emphasized that traditional satellite data often lack the spatial detail necessary for accurate soil moisture estimation, particularly at the field level, and highlighted the importance of integrating ground-based measurements to improve accuracy and representativeness in agricultural contexts. Another study [53] noted that the original spatial resolution of satellite platforms is insufficient for agricultural applications, which require higher spatial detail, suggesting the combination of satellite data with ground-based measurements to achieve more precise soil moisture estimates. In this sense, the spatial variability observed in this study could not be fully captured by the ERA5 data, suggesting that more precise monitoring might require denser sensor networks or higher-spatial-resolution satellite imagery. Overall, integrating ERA5 soil moisture data with ground-based field measurements provided a robust framework for assessing soil water dynamics in the avocado orchard.