Plants do not listen to the radio. But a team of researchers in Greece recently found a way to turn lemons into miniature “radio stations” that can broadcast information about their trees’ moisture content to a smartphone—the first step toward creating what the researchers call an “Internet of plants.”
Scientists had previously attached sensors to trees to measure their water use, but “no other team had created a wireless [radio] network among plants, transmitting information while consuming only a few microwatts and costing just a few dollars,” says project leader Aggelos Bletsas, a professor of electrical and computer engineering at the Technical University of Crete.
The network consists of several basic components: an existing FM radio station, an antenna attached to a lemon growing on a tree, a humidity sensor in the lemon, a transistor connected to an antenna and an FM receiver (such as the kind found on a smartphone). First, the antenna picks up the ambient signal from the FM station. The antenna then passes the signal to the transistor, which is modulated by the humidity sensor. The sensor switches the transistor on and off at a rate dependent on the plant’s moisture level: if the soil is wet or if the atmosphere is humid, that rate is lower; if it is dry, the rate is higher. Finally, the antenna broadcasts this information to the radio receiver on a mobile phone.
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In this way, plants can tell farmers if they are thirsty. “We can literally ‘listen’ to the moisture of the plant, using our mobile FM radio with a €3 [$3.40] sensor,” Bletsas says. “Two of these sensors for every acre on any given farm might change the way we [conduct] agriculture and ‘understand’ plants.” He notes that more sensors may be needed for optimal results, particularly if the field slopes and cannot be watered evenly. Such real-time information could enable better control of air and soil moisture and possibly reduce the use of pesticides and optimize fertilization, the researchers say.
Why go through all this trouble and not just use already common wireless technology, such as Bluetooth? “Not only is our technique less complex, as we are just borrowing ambient signals in the environment,” Bletsas says, but “a Bluetooth-based sensor costs about €22 [$25]. Our ultimate aim is to launch sensors onto the market costing less than $1.”
Others have praised the idea. “Bletsas and his team are revolutionizing environmental sensing using very simple hardware and surprisingly little power,” says Alexandros Dimakis, an associate professor of electrical and computer engineering at the University of Texas at Austin, who was not involved in the research. “Their work could be a transformational Internet of Things technology for agriculture and for monitoring the environment.”
Bletsas and his colleagues have already applied for a patent for their innovative technology in the U.S.
