• Reddit
• Digg
• Facebook
• MySpace
• del.icio.us
• StumbleUpon
• Technorati
• Furl
• Newsvine
• Google Bookmarks

You may also be interested in...

Photo: PureSense
Pure Sense monitoring station powered by solar panel and battery backup

New technologies to control and moderate crop water use have emerged in the past decade and are increasing crop yields. A study published in September 2008 by the Pacific Institute, More with Less: Agricultural Water Conservation and Efficiency in California—A Special Focus on the Delta, reviews the research and, in particular, analyzes four scenarios for improving water use efficiency: modest crop shifting, smart irrigation scheduling, advanced irrigation management, and efficient irrigation technology.

The study notes that regulated deficit irrigation can be an important tool to both reduce applied water and increase revenues. Deficit irrigation applies water below the requirements for traditional, full crop evapotranspiration (the movement of water through the plant and its evaporation).  

Irrigation control technology makes regulated deficit irrigation possible without introducing water stress to crops, if it is used during stress-tolerant growth stages, says the study. For example, it notes that regulated deficit irrigation can be used on pistachios during the shell-hardening phase that is particularly stress-tolerant, while the bloom and nut-filling stages are not. Studies have also shown, the study says, that this technique might improve crop quality, particularly for wine grapes.

David Zoldoske, Ph.D., director of the Center for Irrigation Technology at California State University, Fresno, and a member of Water Efficiency’s Editorial Advisory Board, says irrigation control technologies have been evolving for 20 years, and, in the last five years or so, the innovations have focused on monitoring soil moisture.         

Agriculture consulting companies have been around for some time, explains Zoldoske. In the past, neutron probes were used to measure soil moisture, and reports were provided to growers, but that work was time and labor intensive. The latest technology, created by PureSense, uses their programming experience and a lot of science to develop reporting techniques using real-time information, building on existing technology, he says. 

Photos: Acclima

Irrigation control technology makes regulated deficit irrigation possible.

A soil moisture sensor being laid in the ground

There are two types of smart water application technologies, also known as SWAT-those that monitor soil moisture in the root zone, and those that use weather data to estimate the amount of water used by the turf to adjust the irrigation. Soil moisture monitoring technologies are reviewed here.

The companies profiled illustrate the technologies available for smart irrigation scheduling and advanced irrigation management, including regulated deficit water usage. The profiles were not intended to promote the companies themselves. Seventeen company products have been evaluated by the Center for Irrigation Technology, featuring technologies using both soil moisture and weather data technologies. These reports are available at www.irrigation.org.

Information-Based Technology
PureSense announced an infusion of $4.5 million in venture capital financing with One Earth Capital, in March 2008, at the same time that it unveiled upgrades to its Irrigation Manager software, its core service offering for efficient water use in agriculture. Founded by Craig Buxton and a small team in 2003, PureSense’s technology was incubated as a technology spin-off of NASA technology at NASA’s Ames laboratory. 

In addition to its Jack London Square headquarters in Oakland, CA, PureSense also has a branch at the Claude Laval Water and Energy Technology Center in Fresno, CA.

The company provides ongoing turnkey consulting service to growers of irrigated crops with real-time support for irrigation and water use, featuring Web-hosted software that receives real-time data via wireless communication from its PureSense proprietary monitoring station. Growers can access the system anytime and from anywhere via computer, phone, and PDA devices.

Richard Gates, chief information officer, explains that the company contracts with each grower, evaluates water and irrigation needs, installs field monitoring stations, activates online software, and maintains and upgrades its online tools. Pricing is based on the growers’ acreage, type of soil, crops, and unique field conditions that influence a crop’s performance.

For example, row crops like carrots have shallow roots that require different configurations and shorter moisture probes than permanent crops like fruit or nut trees. Also, a sandy topsoil layer will not hold water, but the clay layer underneath will, thereby requiring deeper moisture probes. This kind of information determines the economics of the service and the most viable cost-effective system.

The monitoring station communicates via a proprietary device to a soil moisture probe that is buried in the soil 18 inches to 1.5 meters, depending on the crop and soil profile. The monitoring station sits on a pole approximately five feet above the surface of the ground up to 30 feet from the probe. It is powered by a small solar panel, 8 inches by 14 inches with battery backup.

The soil moisture probe can read moisture levels every 4 inches at 15-minute intervals 24 hours a day, and the weather components read temperature, humidity, and other climatic variables at the same time, both below and above the canopy of the crop. This raw data is transmitted to the monitoring station, and then by the wireless communicator in hexadecimal language to PureSense’s servers. Here Irrigation Manager software reads it and generates reports and trend charts that can be read by the grower to see, anytime and from anywhere, how their crops are using water and to show them when their irrigation system is on or off, assisting them with fine-tuning moisture levels.

Credit: PureSense

A PurseSense chart maps the amount of moisture retained in the soil. The top row is a summary of measurements of the three depths. The horizontal lines spike up, illustrating increased moisture after irrigation starts, as indicted by the pressure switch marks in the bottom row.

Alerts Improve Efficiency and Sleep
In California, growers worry about frost between midnight and sunrise during the winter months. They must know when to use irrigation water to prevent frost damage, like what hit citrus groves in 2006, explains Gates. When temperatures reach the level he chooses, a grower can receive the automatic alert and turn on the water.

One grower with 10,000 acres has 80 moisture sensor probes and 10 weather stations, explains Gates. Now, he turns the water on only when he receives the automatic alerts from PureSense when the temperature reaches 34˚F.

“It’s a huge leg up, because he’s not watering in late winter and early spring,” says Gates.

Also, certain root diseases, like mold and mildew, are prevented once watering is decreased. This is even more valuable in the case of heat alerts when temperatures are rising rapidly; the ground is sensitive to surface moisture and humidity and can easily activate a Petri dish situation for fungus or mold formation.

Another farmer slept in his field and woke up each hour to check the temperature, says Gates. Now he can sleep in his own bed until 2 a.m., when—and if—he gets an automated alert from PureSense. Another big grower with five irrigation managers never knew if they turned on the irrigation system when the grower told them to. Once he had the PureSense system installed along with pressure switches in the drip lines to indicate when water was going through, he could see the pressure switch signals and soil moisture changes on the trend chart, says Gates-even when he was on vacation in Hawaii. His irrigation managers now know he is looking over their shoulders.

John Kontrabecki is the owner of the TriValley Vineyard in Livermore, CA. The vineyard has been growing six varietals of wine grapes on 100 acres since 2002. Kontrabecki says he was having problems getting the yield he expected. The fruit quality was high, but the volumes of grapes were below expectation. He enlisted PureSense to improve the yield. PureSense installed a moisture probe and monitoring station in each block that grew an individual varietal.

According to Kontrabecki, they discovered that because the plants were grown on a hillside with soil composed of adobe clay, the water was running off. When the soil dries out, it can shrink and damage the root systems. Unknowingly, the plants were being starved for water.

He used to turn his drip irrigation on for about 12 hours and saturate the soil around the roots and shut off the water for a week. Now he irrigates more frequently, but for shorter periods. As a result of this adjustment, moisture stays constant around the root system. The result is that yields have doubled. The vineyard is now producing 4–4.5 tons per acre, up from 2–2.5 tons per acre.

“The vineyard has never looked better,” says Kontrabecki.

This example emphasizes a point Gates makes: “Overwatering is just as bad for a crop as underwatering,” he says. “However, a more important result is that, by carefully monitoring the irrigation system cycles and the soil moisture readings, you can increase the yield of your crop.

“You may be using the same amount of water, but you are producing more food and more value for yourself,” adds Gates.

Automatic Control Technology
Acclima, headquartered in Meridian, ID, has been selling the Digital TDT Soil Moisture Sensor and irrigating with it since 2001. It functions using a patented, digitized time domain transmission signal that company founder, Scott Anderson, developed. 

The moisture sensor measures the absolute water content of the soil under all conditions of temperature and soil chemistry, and communicates with and receives electrical power from the controller. Acclima’s proprietary system allows multiple sensors and other devices to receive power and maintain communications over just two wires. 

The moisture sensor is buried about 2–3 inches in the soil and wired to the valve box on the irrigation system. The cable containing the wire is buried 8 inches deep in the soil. The customer then has complete control over operation of the irrigating system and can modify its operating hours.

Acclima also sells five models of closed-loop irrigation control systems, each paired with its sensor. They are capable of covering six to 12, 24 to 36, or 64 zones depending on the model and are designed to allow for one sensor per uniform zone. 

Acclima’s suspended time controllers allow timers to be set up based on the amount of precipitation needed. The timer has set start times and durations, but the system will be inhibited if there is sufficient moisture in the soil. For example, the SCX suspended cycle add-on device can be used on any 24-V timer. It can interrupt conventional timers, and do auto setup and performance reporting.

Alternately, with water-on-demand irrigation, the controller requires no schedule programming and turns water on only when the soil moisture level falls below a set threshold. The high-end commercial controllers are also capable of controlling watering within restrictions set by local governments.

For new systems, a single wire pair or multiple wire pairs can be used to mark the limits of the property and interconnect all sensors, valves, flow meters, and such attached to that two-wire network. It conveys 24-V power to the valves and other devices on the system, and it conveys signals to maintain communications with the same devices.

Acclima also offers irrigation manager software. It allows multiple controls and monitoring of irrigation controllers from a central location. Maps of sites can be imported, and the irrigation system can be viewed including zones. Reports and sensor graphs are also available.

Saving Water While Improving Plant Growth
Kingsley Horton, western states sales manager for Acclima, describes a study done at a Florida housing development that had been warned by local authorities about exceeding permitted water limits. The authorities threatened to shut down the development. Two different contractors installed Acclima systems, and water usage was tracked. The Acclima system reduced water usage 62%, compared to areas where irrigation timers were used with no Acclima systems.

At the Idaho State Capital, Horton says the company installed one controller with three sensors, at a cost of $2,400. That controller saved enough water to pay back the cost in 3.8 months, despite a leak caused by a broken pipe behind the water meter causing runoff into the street all night. Apparently, the managers had opted to not install flow meters that would have shut the water off. Horton says they have changed their minds about the advantage of a flow meter, since it could have saved even more water.    

Roger Water, a landscape architect specializing in water and soil management, installs Acclima smart controllers regularly. He originally installed controllers that use weather data and ran into various kinds of problems. The radio that needed a signal sent to it would lose the signal, antennas and radios broke, and wire contacts went bad on solenoids.

“I need to have customers not be aware of the irrigation system,” he says.

And when things break, the customer becomes aware. In a number of gardens and landscaped residential estates, he replaced those systems with Acclima’s probes and controllers, and got much fewer callbacks.

However, Water says he would install the weather-based wireless WeatherTRAK system in areas where there is too much hardscape to run the wires needed for the Acclima system.

“You do save an awful lot of water,” says Water, of the Acclima system. He recently replaced a weather database system that had been in place for three to four years, with an Acclima controller at a winery in Napa, CA. The owner is now saving one million gallons of water annually.

These savings came after Water cleaned out the irrigation system a year ago, moving heads around to improve coverage, and reducing the number of controllers from six to four. Water usage plummeted from 8,000 gallons per day to 3,700 gallons per day during a period that included a 110˚F heat spell.

When he installed the Acclima system four to five months ago, he reduced the number of controllers further, to two. The owner told him the plants have never looked better.

John Paz is a grower-manager at Milano Flower Farm that grows cut flowers and cut greens in Carlsbad and Oceanside, CA. Cut greens are plants such as myrtle, boxwood, and ruscus. Paz installed one Acclima controller and six probes in October 2007 in the 325-acre Oceanside farm he manages. Over 20 types of plants are grown and all take different water requirements.

“The biggest thing we’ve learned is how to do leaching,” says Paz.

The well water is high in sodium, and he was increasing the amount of water to leach it out, but he wouldn’t see any increased moisture in the probes unless it rained heavily. The reason? Water was running off the fields. The effect on plants was burned leaves-something unacceptable in the cut flower and greens business.

Now he breaks up the watering and avoids runoffs. Salinity has dropped as a result. The water schedule was modified from six hours straight, to three hours in early mornings and three hours in late afternoon. “It’s a mindset about continuous watering,” he says. “This learning was due to the probe.”

The next step for Paz and his colleagues is an experiment. They are adding three more probes in one field. One part of the field will get one percentage of water while another part of the field will get a different percentage of water, so they can determine how much water the plants actually require.

Horton says customers in Europe, South Africa, and Australia have installed the company’s technology. A new Italian distributor has sold 300 systems without technical support. The systems are very popular in Florida; in hot pockets in Michigan, Minnesota, Ohio, and Wisconsin; throughout the West; and in Texas.