Graphene Oxide Array for In-Depth Soil Moisture Sensing toward Optimized Irrigation

A capacitive approach is employed to find moisture of the soil at various depths (4.5–20 cm). The sensor probe having dimensions 22 × 4 × 0.5 cm3, embedded with a series of five microsensors (scalable according to the need), is developed using a graphene oxide (GO) sensor array. The measurement electrodes were designed in an interdigitated manner having eight pairs of comblike-shaped fingers with 100 nm thickness and 90 μm spacing. It has been observed that, for black soil, all of the microsensors displayed response in the range of 500–550% when the soil water content is varied from 3.2 to 55.5%. The graphene oxide-based array probe sensor (GO-APS) shows fast response and recovery time of 140 and 20 s, respectively, for 10% soil moisture samples. The soil moisture profile has been monitored up to a scale of 20 cm depth using the fabricated design. In-depth soil moisture profiling shows a maximum deviation of ±2.4% compared with a standard oven-drying method. The lump formation effect in soil mass showed a maximum deviation of ±4% for the GO-APS array. This robust and low-cost GO-APS with high sensitivity is promising for technological advances in agricultural application.