Dataset for: Multidepth Soil Sensing with Embedded Hydrothermal Stress Index Reveals Stratified Stability in Hardpan-Limited Tropical Spodosols

This dataset contains multidepth soil hydrothermal measurements collected from a field-deployed smart sensing system in a hardpan-limited tropical Spodosol oil palm plantation in Central Kalimantan, Indonesia. The dataset includes volumetric soil moisture content and soil temperature recorded at three depths (0–10 cm, 10–42 cm, and 42–68 cm), along with atmospheric variables including air temperature, relative humidity, rainfall, and solar irradiance. The data were used to develop and validate an embedded Hydrothermal Root Zone Stress Index (HRZSI), a normalized state-based indicator representing depth-resolved hydrothermal stability, persistence, and nonlinear response behavior within the soil profile. The monitoring period spans 225 consecutive days under rainfed conditions. The dataset supports analysis of vertical hydrothermal stratification, variance compression, rainfall–moisture lag response, thermal–moisture coupling, and nonlinear state-space behavior in hardpan-constrained tropical soils. It is intended for reproducibility, validation, and further development of smart soil monitoring and precision agriculture systems.