Plants tell sensor when they need a drink

University of Colorado researchers have developed a prototype that monitors when crops need to be watered. The current prototype still uses wires but will eventually be outfitted to rely on RFID.

This technology allows not only the data, but also the power to be transmitted wirelessly, eliminating the need for batteries.

The sensor would be clipped permanently to a leaf during the growing season to monitor moisture content and chemical signatures that can indicate when the plant is undergoing water stress.

The chemical signs, such as an increase in salt and sugar content in the cells, occur much earlier than physical signs, such as drooping leaves, that many farmers rely on now.

Because it can only transmit a signal about half a metre away, the RFID tag can do one of two things with the data: it can transmit it to RFID tags nearby, which would then push the signal along to other tags in the network until the data reaches home base.

Alternatively, it can deliver the signal to a nearby base station, which would have enough power (using a battery or solar panel) to transmit the data directly to the farmer's computer.

Software on the computer would then analyse the data and could alert the farmer by email or text message. Or the computer could be set up to go one step further and automatically turn on the irrigation system.

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