Tech corner


Using the power of IoT to improve irrigation water management


By Yossi Osroosh, PhD, and Diganta Adhikari, PhD E


fficient management and optimization of farm inputs will be key to feeding the growing world


population. However, managing these inputs, such as irrigation schedules, will require real-time data from networks of soil, crop and weather sensors at a desired resolution and reasonable cost.


Wireless sensor networks could conveniently collect soil and crop data in granular detail from various parts of the agricultural field to capture the spatial and temporal variability that exists in the field. Similarly, wireless actuators could also be used to turn irrigation valves on/off remotely based on real-time information from the in-field sensor network. For example, when soil moisture sensors and near-infrared sensors detect a preset threshold value, the in-field sensor network could either send an alert to the grower to initiate or stop an irrigation event or, alternatively, send the data wirelessly to an actuator to turn irrigation on/off autonomously.


Existing or emerging sensors and actuators could be made wireless with the aid of a wireless communication device. This need has led to the development of low-power wide-area networking, or LPWAN, within the “internet of things” technology network. LPWAN technologies are intended to connect low-cost, low-power sensors to cloud- based services. Today, there are a wide range of wireless and IoT connectivity solutions available, raising the question of which LPWAN technology best suits the application.


Here are the scenarios for implementing IoT: 1) buy a sensor that will connect to a wireless network that you own (i.e., customer supplied like Wi-Fi, Bluetooth), 2) buy the infrastructure (or at least pieces


6 Irrigation TODAY | April 2018


of it) to install on-site (i.e., vendor-managed LPWAN such as LoRaWAN or Symphony Link), or 3) rely on the infrastructure from a LPWAN network operator (e.g., LTE Cat-M1, NB-IoT, Sigfox, LoRaWAN).


LPWAN technology fits well into agricultural settings where sensors need to send small bits of data over a wide area while relying on the battery to last multiple years. The low-power and range features distinguish LPWAN from Bluetooth, ZigBee or traditional cellular networks with limited range and higher power requirements. However, like any emerging technology, certain limitations still exist with LPWAN. For example, in real agricultural settings, field tests have shown LoRaWAN gateways (or the data communication device) to have a range of up to 4.5 miles over a corn canopy, but that only occurred when gateways were placed 33 feet above the ground. With gateways placed at 10-12 feet above ground, the range was found to be about 0.5 miles.


Managing farm inputs will require real-time data at a desired resolution and reasonable cost.


A one-to-many approach to architecture is common with respect to wireless communication. Existing wireless technologies like Bluetooth LE, Wi-Fi or ZigBee can be used to collect in-field data. In this case, data could be transmitted in and out of the field through existing communication infrastructure like a traditional cellular network (e.g., 3G, 4G) or LAN. Alternatively, private or public LPWAN solutions such as LoRaWAN gateways or cellular IoT can be used to push data to the cloud. For example, a grower can have a network of soil moisture sensors in the field equipped


with radios. These sensors wirelessly report their measurements back to a datalogger installed in a corner of the field at no cost. The datalogger can use a SIM card and regular mobile data plan to send data to a remote computer.


Most LPWAN technologies (e.g., Sigfox and NB-IoT) currently have a very limited network coverage in the United States. For example, we tested a LoRa device for


End user application


Field nodes


Public/private LoRa gateway


Network server, passthrough and visualization platform


Example: Data flow through public/private gateway infrastructure


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