Quick Look
Iowa State researchers have developed a "lab-on-a-drone" that can fly to remote, marshy areas of farm fields and collect real-time measurements of nitrates. The resulting maps of nutrient concentrations could provide "an evaluation critical for both economic and environmental sustainability," according to the researchers.
AMES, Iowa - The underground tiles that drain farm fields can release water into remote and shallow waterways. It's not always easy to get out there with equipment to sample and test for agricultural chemicals such as nitrate.
Improving testing capabilities is important for managing nitrate levels in drinking water, which are federally regulated, and in waterways where nitrates can contribute to marine dead zones.
"Lab-on-a-drone" technology, as described in a recent paper published by the scientific journal ACS (American Chemical Society) Sensors, can quickly fly to those remote drain outlets in agricultural watersheds and, within 7 minutes, collect a water sample with a pump and hose, run the sample through a sensing system, record accurate nitrate levels, flush the sample and fly on to the next test site.
"The user-friendly, cost-effective, and energy-efficient payload enables real-time sensing, allowing researchers to map nutrient concentrations and helping farmers determine whether fertilizer is being effectively retained in the field or lost to surrounding waterways - an evaluation critical for both economic and environmental sustainability," wrote a team of Iowa State University researchers led by Jonathan Claussen, a professor of mechanical engineering. (See sidebar for the full research team.)
The U.S. Department of Agriculture's National Institute of Food and Agriculture is supporting the project with a three-year, $590,000 grant. The U.S. National Science Foundation and Iowa State's Digital and Precision Agriculture Applications program also provided support.
Looking for a new way
Claussen said members of the research team, including some who study water quality, wondered if drones could be an effective way to access and test remote waterways that are difficult to reach in person or by boat due to marshy terrain, low water levels or physical obstructions.
The researchers asked a team of engineering students to study drone-based solutions as part of a senior design project. The students came up with a prototype design that demonstrated drones could be used for what the researchers call a "collect-and-sense" system of water quality testing, rather than merely flying out to collect samples for later lab tests.
The implications of a lab-on-a-drone for water quality testing?
"This project has the potential to increase the resolution of water monitoring without the need to invest in expensive and stationary sensors," said Michelle Soupir, a professor of agricultural and biosystems engineering and an associate dean for the Graduate College who identified and coordinated field-testing sites for the project. "The drone could allow sampling from sites that are difficult to access, especially during certain weather conditions."
Sensors for the job
Claussen and his research group have a long record of developing sensors for agriculture, food safety and health applications. He, for example, is contributing sensor expertise to a national industry-university research hub called the Center for Soil Technologies, or SoilTech, based at the University of Southern California. The U.S. National Science Foundation is supporting the center.
For the lab-on-a-drone, Claussen's research group started with commercially available screen-printed carbon electrodes, to eliminate electrode maintenance and to set a standard for the data collected by the drone system. Researchers developed their own membrane that allows nitrate ions to pass through and produce an electrical signal that can be measured.
Controlling the sensing operations are electronics designed and built by Nathan Neihart, an associate professor of electrical and computer engineering, and his research group. The electronics run the water sampling pumps, the sensing system and store the resulting measurements on a memory card.
Total cost of the sensing payload, including a sensor, a pump system, electronics and mounting hardware? Less than $135, the researchers wrote.
A tool for precision agriculture
Now that the researchers have demonstrated their lab-on-a-drone for nitrate testing, they say other applications are possible.
"Future modifications could incorporate sensors for detecting pesticides and bacteria, promoting more responsible pesticide use and ensuring that irrigation water is free from microbial contaminants that could lead to costly food recalls," the researchers wrote. "Hence, we believe this lab-on-a-drone system can serve as the foundation for a versatile platform capable of supporting a wide range of real-time environmental monitoring applications in precision agriculture."
Even with years of experience developing agricultural sensors - including some that are buried in the ground and some that are attached to plant leaves - real-time sensing aboard a drone is a first for Claussen and his research group. It's a promising direction and, he said, "a new adventure for the lab."
