Arduino-Based Monitoring of Soil Temperature under Contrasting Substrate and Rainfall Conditions

Soil temperature dynamics play a crucial role in various soil processes and plant development. In this study, two experiments were conducted to evaluate the effect of structural and climatic conditions on soil temperature, using a custom-built Arduino-based data logging system. Experiment 1 (Julian days 203 - 257) compared field soil and potted soil under rainy conditions, while Experiment 2 (Julian days 258 - 278 for Rain and 279 - 338 for No Rain) evaluated potted soil versus potted sand under both rainy and dry periods. Interior and surface temperatures were recorded every 40 minutes using buried and exposed sensors, and daily minimum, maximum, and average temperatures were analyzed. Results from Experiment 1 revealed that interior soil temperatures in pots were significantly higher (up to 32.26˚C) and minimum temperatures lower (down to 13.4˚C) compared to field soil. This indicated greater thermal variability in pots, even under rainy conditions. In Experiment 2, no significant differences were observed between sand and soil within pots under rainy conditions; however, temperature values differed markedly between climatic conditions. Under dry conditions, interior maximum temperatures exceeded 34˚C, while minimum temperatures dropped below 8˚C. Additionally, in both experiments, surface temperatures were generally higher than interior temperatures. The data suggest that structural configuration (pot vs. field) and rainfall presence are the primary factors influencing soil thermal behavior, rather than substrate type. The sensor system proved reliable for detecting both thermal contrasts and similarities, providing a valuable tool for evaluating soil temperature under varying environmental conditions. Although each treatment was represented by a single container due to equipment constraints, the findings lay the groundwork for future studies incorporating greater replication and spatial variability.