Nine Things You Need to Know About Irrigation Sensors

Since 2009, a diverse team of researchers and manufacturers has been involved in a project funded through the Specialty Crop Research Initiative that is focused on how ornamental growers could potentially save both money and water through the use of irrigation sensors placed directly into the soil.

The goal of the program is to provide growers with real-time information on environmental conditions within the soil, and allow them to schedule irrigation based on specific crop requirements.

Marc van Iersel, a horticultural physiology professor at the University of Georgia, is one of the researchers involved in the project. During AmericanHort’s Production Technology Conference in October, van Iersel gave a presentation on how irrigation sensors can be used in commercial settings. Based on his presentation, here are nine things you need to know about using irrigation sensors.

The Benefits Are Clear, If You Use Them Right

On the surface, irrigation sensors can provide four basic benefits: financial savings, improved plant quality, reduced shrink, and (when you tie the first three benefits together) increased profits. However, the benefits go much deeper than that.

There’s a Roadmap in Place

Researchers involved in the project have made a great deal of progress in giving growers a plan on how to make the best use of irrigation sensors. In particular, they have:
• Developed wireless sensor networks, with monitoring and control capabilities (hardware)
• Developed a graphic user interface, for intuitive decision making (software)
• Developed guidelines to manage irrigation
• Quantified the impact on production (quality, fertilization, runoff)
• Determined the economic impact of better irrigation management

Know Your Components

There are two main components that go into a wireless sensor network: hardware (sensors, nodes, and valves) and software (used for data visualization and decision making). The sensors themselves come in several different models, and can measure how much water is present in the soil and how much of that water is actually available to the plant (water content versus water potential). There are different sensors for each of these measurements, and while the quality of the technology has improved greatly over the years, as Van Iersel says, you get what you pay for.

The Potential for Water Savings Is Significant

“We found that we can save water, improve plant quality, and promote faster plant growth, which leads to more turns, fertilizer savings, and long-term environmental savings,” van Iersel says.

How much water savings can you expect from this approach? Try 40% to 85%, van Iersel says.

“In one instance, a 50% reduction in irrigation saved more than 43 million gallons of water for a nursery in 2012,” van Iersel says. The nursery also saved $6,500 in pumping costs.

There Will Be Some Challenges

van Iersel notes that most of the research has involved overhead and drip irrigation, although Damatex has developed a system for booms, collaborating with Visser. Some operations may also be limited by their well or pump capacity, but this is actually where a sensor-based system may help, because it reduces water use. But the system does need to be smart enough to not open too many valves at the same time, if overall irrigation capacity is limiting.

More Stems and More Money

The charts in the slideshow above an economic analysis of six years of production data, three years before implementation of sensors (2007 to 2009) and three years after implementation of sensors (2010 to 2012). Cultivar groups are grown at different times of the year. Most cultivar groups showed a significant increase in the number of stems produced after sensors were used, compared to pre-sensor use. The cultivars in Group 1 were produced in the winter, while Group 4 crops were grown in the summer.

When translated to dollars per stem, more charts in the slideshow highlight that price (quality) was significantly improved in Group 3 and Group 3 and 4 (late spring/summer) cultivars, showing the benefit of better irrigation.

… And More Profits

The bottom line, van Iersel says, is that significant increase in total stems per year and net revenue were seen after sensors were used for irrigation (fertigation). The decrease in electricity costs is most likely due to reduced irrigation frequencies, as shown in one of the charts (Economic Analysis: Annual Profitability).

Payback may even be possible within a month. Results of an economics analysis by Erik Lichtenberg, a Professor in the Department of Agricultural and Resource Economics at the University of Maryland, at one nursery showed a potential profit increase of 156% in gardenia production. By far the most important benefit was the shortened production time (which reduces production costs and allows for another crop to be started sooner).

Reducing shrinkage by preventing disease problems was significant, but much less important. Part of the analysis is theoretical; the nursery might not be able to fully realize the additional profits. But there is no doubt that the economic impact was substantial (and really got the nursery’s attention).

Grower Trials Demonstrate Real-World Performance

Here’s just a few examples of what growers who were involved in the research trials experienced:
• Flowers by Bauers, a producer of cut snapdragons in Jarrettsville, MD, experienced increases in both yield and quality. According to the company, the system paid for itself in less than 16 months.
Foertmeyer & Sons in Delaware, OH, which uses boom technology in its greenhouses, was looking for a control system that worked from the ground up.

“I’ve been a big fan of Decagon EC5 soil moisture sensors from Damatex for many years, and what I wanted was a boom that could be controlled by these sensors,” says Matt Foertmeyer of Foertmeyer & Sons. “With these booms, I’m able to program individual zones for each separate crop in my bays, and then assign a separate EC5 soil moisture sensor to control the irrigation of these separate zones. With the soil moisture sensors, I can set a crop of verbena to be grown more dry than a crop of calibrachoa in the same bay, and once a plant dries down to its given set point, the boom then automatically kicks on and irrigates that crop.”

• Willoway Nursery in Avon, OH, has tested the system, as well. According to Willoway’s Tom Demaline, it works, although there might be challenges in implementing it on a larger scale.

There Are Low-Cost Versions, or You Can Make Your Own

For example, Bennett’s Creek Nursery in Smithfield, VA, has developed its own Arduino-based sensor network (a step-by-step approach is outlined on Instructables.com).

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