Controlling the irrigation process in agriculture through elongated TDR-sensing cables

In this work, time domain reflectometry (TDR) is used in conjunction with an innovative type of low-cost, wirelike diffused sensor for diffused soil water content monitoring in agriculture. Thanks to its wire-like configuration, these passive, maintenance-free sensors can be rolled out and buried along the perimeter/path to be monitored (for example, along a row of plants/trees). A single sensor can be long up to 150 meters, and several sensors can be simultaneously installed in a large area, thus creating a diffused sensor network which can be controlled through a single measurement instrument. To assess the practical feasibility of the proposed TDR-based system, a practical experiment was carried out by employing a bifilar, wire-like sensing element (SE) for monitoring soil water content in a watermelon cultivation. For comparative purposes, also in view of continuous remote monitoring, measurements were carried out through three TDR instruments with different specifications and costs.