Smart-agriculture strives to use technology to increase the quality and quantity of agricultural output while guaranteeing sustainability. Key to achieving these objectives are “connected” sensors that monitor a wide variety of farms’ health indicators. Arguably the most important of these indicators is the soil moisture content. Indeed, such measurements must be acquired with a high temporal and spatial resolution so as to realize efficient utilization of irrigation resources. The most commonly utilized system for soil moisture content measurement relies on a network of conventional contact sensors placed inside the soil. However, achieving high spatial resolution with this approach requires the sensors to be spread throughout the farm, thus rendering the approach infeasible for vast fields. An alternate approach is to use ground penetrating radars mounted on mobile platforms. However, these platforms are bulky and expensive, and thus infeasible for resource-constrained farms such as those in Pakistan.
The objective of this initiative is to develop a soil moisture sensing system that is scalable to vast fields, achieves good spatial resolution, and at the same time is cost-effective. Exploiting the fact that the reflection properties of radio frequency (RF) waves are a function of the moisture content of the reflecting surface, we intend to develop a sensing system composed of an off-the-shelf WiFi transceiver transmitting and receiving radio signals in the unlicensed ISM band. Such an RF-based system is all-the-more attractive since the system could make the moisture measurements using the same piece of WiFi hardware that it employs for communicating the measurements to a centralized smart farming controller. In addition, since WiFi transmissions are typically made with devices that are cheap and light, the system, when mounted on a mobile platform, would promise cost-effective soil-moisture measurements with high spatial resolution.