Sensor Network Has Avocado Farmer Seeing Green

High water costs made Kurt Bantle's avocado farm financially untenable, but after optimizing his irrigation system by using a network of sensors linked to an IoT network, he was able to slash his water costs and recoup his investment in just six months.
By Mary Catherine O'Connor

Rather than trying to optimize the ZigBee sensors, Bantle decided to evaluate different technologies. At the time, low-power, long-range radio networks (LPWAN), operating in an unlicensed ISM band, were starting to hit the market and Bantle was intrigued by LoRa, a LPWAN protocol developed by IBM, Semtech and more than 10 other technology and telecommunications providers.

The LoRa network that Bantle deployed has been running for roughly one year, and comprises 20 moisture sensors that measure the soil's water level based on its electrical resistance, as well as 10 thermistors. Two moisture sensors (one positioned near the topsoil and another set more deeply) and one thermistor are wired to each microcontroller, which is paired with a LoRa radio, provided by Multitech.

Every 10 minutes, the sensors transmit their readings over the LoRa radio to a gateway, provided by Multitech. The gateway contains an embedded SIM (eSIM) provided by Spirent partner Oasis. Embedded SIMs are chips that are soldered into devices and programmed, over the air, with a SIM profile that allows the device to be commissioned to a specific cellular network but which can later be overwritten with a different operator's profile. (Remote SIM provisioning is an approach that the mobile phone industry association GSMA developed in order to improve the versatility and lifecycle of machine-to-machine hardware that may be deployed in large quantities or remotely. This would make the task of physically replacing SIM cards impractical in the event that the organization responsible for the network would like to switch to a different cellular operator.)

The moisture data is collected in a cloud-based software platform that Spirent is preparing to commercialize, modeled on the system that Bantle developed. When the moisture level falls below a set threshold, the platform sends the message back down to the gateway, over the cellular network, and the gateway relays a command to the LoRa-based valve controllers on the irrigators. The sensors continue to transmit moisture and temperature data to the cloud-based software, via the gateway, and once a sufficient amount of water is applied, the system closes the irrigation valves.

To determine his irrigation schedule, Bantle previously relied on a local weather station and the California Irrigation Management Information System (CIMIS), which calculates evapotranspiration rates for zones across the state, which farmers use to determine how much they should irrigate. But now he uses the sensor network to allocate the water.

So far, the network has paid significant dividends, Bantle reports. His goal was to reduce his water consumption by 50 percent, but he is actually using only a quarter of the water he had been using prior to deploying the sensors, because he also decided to rip out the mature trees in the orchard and replace them with new ones, which require less water overall. Still, he is bullish on the technology and believes that—even as the trees grow and demand more water—it will enable him to maintain a far more water-efficient operation than he ran prior to the network installation. "The trees are not at full maturity yet, but when they are, we'll be at 50 percent of the water we used to use, or maybe even better."

All told, Bantle spent $8,200 on the hardware (the LoRa radios, the sensors, valve controllers, a LoRa gateway and a cellular backhaul), plus his monthly cellular subscription cost of $60. Yet, by reducing water consumption by 75 percent, he was able to achieve a return on his investment in just six months.

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