Take Control

Landscape contractors can’t control the weather, but they can at least attempt to gauge its effects on properties and use these observations to make educated assessments regarding their irrigation practices. Weather stations and controllers are designed to fine-tune this process by combining technology with basic earth science.

Weather stations, though common in agriculture and some larger commercial markets, have not yet made a significant break into the residential landscape market. But many weather station manufacturers are turning their attention in that direction, hoping to reach contractors in the residential market and show them how the instruments, in conjunction with controllers, can boost water efficiency and regulate the operation of a property’s irrigation system.

Neal Israelsen, marketing director, Campbell Scientific, Logan, Utah, explains that weather stations collect data on weather, soil and wind conditions that can be translated into numbers and input into predetermined mathematical calculations that are used to regulate irrigation output, start-times, stop-times and give a general idea of any property’s external conditions. "A weather station is made up of what we call a day logger," he says. "It’s a small computer that usually runs on a 12-volt battery and measures the electrical signals coming from built-in sensors, converting them to temperature, relative humidity, wind speed, wind direction, solar radiation and rainfall. Those are the main parameters that most everybody measures."

Israelsen says that in many cases data is collected by a weather station’s sensors once every five seconds. "It accumulates all of that data into hourly data that is then downloaded to the computer system."

Contractors use weather stations in a variety of ways to determine watering needs. "Data from soil moisture sensors are the most direct way of knowing if there is sufficient moisture to meet turf needs," says Mike Mueller, marketing manager, Spectrum Technologies, Plainfield, Ill. "Weather station data can also be used to calculate evapotranspiration (ET) using commonly available universal or region-specific mathematical algorithms. The algorithms calculate the ET demand of a specific reference area, such as grass. ET for that specific area is then calculated with a multiplicative factor called a crop coefficient. Irrigation scheduling is then based on the replacing of the water that has been removed from the soil profile."

Mike van Bavel, president, Dynamax, Huston, Texas, explains that some weather stations are completely automated electronic recording and computing devices with sensors for solar radiation, temperature, relative humidity and wind speed. "These four factors are responsible for driving the ET need," he says. "As the sun gets hotter and the temperature rises, water is consumed faster by plants and there is greater evaporation from the soil." Van Bavel says that this information, in many cases, is communicated electronically to remote controllers, which adjust the water application in proportion to ET of that property.

Israelsen explains that many companies integrate weather systems in with their irrigation control systems. "They get the weather data and from that data they calculate the ET rate," he says. "They’re using science to give them an idea of what is happening on their property – what weather parameters are occurring – to come up with a rate of water loss. That way, they can program into their irrigation system how much water is needed to replace what has evaporated off."

Mueller explains that this communication often occurs through additional equipment. "Because the weather data is in the form of electronic signals, software and hardware can be integrated to interface with a control device," he says.

According to Mueller, the price of a weather station can range anywhere between $250 and $1,600. Israelsen says that some, industrial-grade weather stations might sell for $4,000 to $4,500. "Larger research-grade weather stations might sell for $8,000 to $12,000, depending on the market channels you go through," he explains. "There are cheaper ones that get down to $300 or $400, but if you’re really going to use it to maintain a property – some of the $1,000 models don’t even last very long."

Mueller says the price of a weather station usually depends on type, number of parameters that must be measured, sensor accuracy, whether or not data is logged, and finally, method of communication. "Method of communication refers to whether or not the information can be read, downloaded manually or is accessible from a remote location via radio signals, telephone modem or Internet." Mueller goes on to explain that data logging and remote communication options require software to facilitate the interface with a PC. "The irrigation controller interface would be another, additional charge," he says.

Van Bavel points to controllers as the other important component for a comprehensive irrigation system. He explains that controllers are responsible for delivering the irrigation water to the property through automation in an organized, efficient and cost-effective manner. "All controllers enable a sequence of irrigation valves so the full water pressure is applied to emitters in a zone, one station at a time," he says.

Van Bavel explains that up to three years ago all controllers fell into basically two categories: electromechanical and microelectronic. "The electromechanical controllers have motor-driven timers with mechanically activated switches," he illustrates. "Essentially, each timer sequentially selects a number of valves to turn on for a fixed period over a weekly schedule."

"In microelectronic controllers, the timers have the same number of station output controls, but the user may program multiple start times per day, easily vary the time each valve (station) is turned on, and alternately program even and odd days," van Bavel explains, adding that this type presents the contractor with significantly more flexibility for the schedule and the creation of programs.

The electronic controller has bolstered reliability, van Bavel says. "Liquid crystal displays and LED display programs, timing and status information contribute to this," he says. "The microelectronic irrigation timer is easy to operate with single station water start and multiple station single cycle watering included as standard features."

Electromechanical controllers are generally less expensive than their microelectronic counterparts averaging from $75 to $150, according to van Bavel. "They’re prone to wear and tear, consistent with a large number of moving parts, an electric clock motor and electromagnetic relays," he says, adding that before microcomputer technology offered an alternative, these prices were the standard for any controller on the market.

By comparison, a microelectronic controller generally has more built-in features to offer. "Their prices range from $100 for retail-market controllers to $500 for more sophisticated commercial controllers," van Bavel adds.

The author is assistant editor for Lawn & Landscape magazine and can be reached at wnepper@lawnandlandscape.com.