Design and Performance Evaluation of a ZnO/TiO₂ Nanocomposite Sensor for Soil Moisture Measurement

Soil moisture is an important soil quality indicator (SQI) which requires continuous monitoring to improve the overall soil and crop health. Advances in technology have led to the development of various sensors for soil moisture measurement. Among these, sensors based on nanomaterials are gaining prominence as an inexpensive and efficient alternative. This work presents a low-cost soil moisture sensor based on ZnO/TiO2nanocomposite. The sensor is fabricated by combining the nanocomposite with ethyl cellulose and depositing the material on an FR4 substrate. This allows direct insertion of the sensor into soil as the nanocomposite remains adhered to the substrate. The sensor shows a monotonic increase in capacitance with increasing soil moisture, achieving maximum response values of 514.16%, 329.42%, and 233.66% for silt loam, loam, and clay loam soils, respectively, at 1 kHz, corresponding to gravimetric water contents (GWC) of 34.75%, 28.70%, and 37.75%. Additionally, it exhibits a low hysteresis, fast response time of 7-9 s, strong repeatability and lowest mean absolute error (MAE) of ±1.60% in comparison to the standard gravimetric method.