Dr. Marc van Iersel: Soil Moisture Sensors

  • United States

Affordable Soil Moisture Sensors

More Crop per Drop: An automatic irrigation system based on reliable and real-time indicators of plant water needs

Agriculture accounts for 70 percent of freshwater use worldwide. Current irrigation practices—from greenhouses to farms—rely on imprecise indicators of when (and for how long) plants should be watered. For example, ornamental growers typically determine plants’ watering needs by picking up a pot to see if it’s light or heavy, or sticking a finger in the soil to detect moisture. Others merely put irrigation on a timer, which waters plants whether they need it or not. Most large-scale agricultural operations utilize similarly inefficient irrigation techniques.


According to some estimates, irrigated plants tend to receive 5–20 times more water than they can actually use. Over-irrigation results in both increased strain on already scarce water supplies, and increased water pollution due to nutrient-rich run-off, which leads to surface-water algal blooms and groundwater contamination. Despite these environmental and health concerns, growers would rather err on the side of over-watering rather than risk the possibility that crops will die or underperform due to water stress.


Professor van Isle is collaborating with other faculty from the University of Georgia to develop affordable soil moisture sensors as part of a multi-institute research initiative (called Smart Farms) to save water, increase efficiency, and reduce the environmental impacts of plant production, while simultaneously maximizing potential growth. A network of sensors directly measures variables both in the rooting environment and from the aerial environment. Irrigation is then automatically activated according to changes in soil moisture as plants take up water.

“This is the next generation of tools to precisely monitor and control water applications based on actual plant needs in order to optimize growth and minimize environmental damage due to leaching and runoff” —Marc van Isle, PhD, Professor of Plant Nutrition and Physiology
The collaborators on this innovation work closely with growers and use their feedback to guide development of the system. Preliminary findings in commercial applications have revealed water savings of up to 83%. These results have significant implications for not only water-use reduction, but also for the protection of ground and surface water supplies due to less run-off.


The goal of this innovation is to provide growers with cost-effective tools that can be used to reduce inputs, increase profitability, and encourage sustainable practices in order to conserve water and protect the environment. At this stage the focus is greenhouses and nurseries, but the system will eventually be applicable to agriculture and landscaping.

“We hope in the long run that we can come up with a simplified version that can be used in developing countries where water is very limited” —Marc van Isle, PhD, Professor of Plant Nutrition and Physiology
Next steps involve developing a set of best management practices, improving the hardware and software interface, determining the appropriate ratio of sensors per plant or per unit area, and designing a method for dealing with the tremendous amount of data that will be collected from these sensors. The goal is to develop a simple-to-use interface that can eventually be accessed by growers from their mobile phones. Additionally, it will be important to understand the sociological aspects of design and marketing in order to ensure that this new technology is accepted by the industry at large, and adopted by growers, some of which may be resistant to change. While the evolution of the Soil Moisture Sensors will require its own set of solutions, the effort must be coordinated with the overall development of the complementary technologies of the Smart Farm initiative including wireless sensor nodes, simulation models to predict real-time water use for large-scale operations, and economic models to quantify both the private and social benefits of reduced water use and pollution. Professor van Isle’s goal is to have commercially available systems by 2014.