FEATURES
Eye on the Sky

by Aaron Johnsen

Manage your course with an on-site weather station

Weather affects nearly every aspect of turf and landscape management. Knowing how a site responds to weather conditions can influence future management practices. Environmental information has come a long way from the days of the local meteorologist. Superintendents now have access to weather forecasts, radar images, current weather conditions and historical weather conditions. Using environmental monitoring technology on your site can provide site-specific real-time and historical weather information.

Weather stations were placed near several golf greens to determine the light quantity difference in tree shade and full sun. Light quantity was correlated with turf quality to determine the optimum light quantity for cool-season turfgrass golf greens. Photo by Derek Settle.

Just as the availability of weather information has improved drastically, so has the equipment needed to collect weather data. It is now affordable to invest in an on-site weather station. A major benefit of on-site weather stations is that they allow the collection of data in microclimates, which are areas where the weather is significantly different. On a large scale, Arizona and Minnesota have different climates. Microclimates exist on a much finer scale. Some examples of microclimates include the highest elevation point on a golf course, the lowest elevation point, a green surrounded by trees and a tee in the open. By collecting data in microclimates, a golf course superintendent can make informed management decisions that will better fit that specific environment.

A complete weather station with temperature, relative humidity, rainfall, wind speed and direction, solar radiation and leaf wetness sensors. Photo courtesy of Spectrum Technologies, Inc. Irrigation needs can be adjusted to account for rainfall. Photo by Rich Redles.

Many courses already have an on-site weather station tied into their irrigation system. These weather stations provide useful and accurate data if maintained properly. There are effective weather stations available that do not tie into an irrigation system. Before deciding on a specific weather station or environment monitoring sensor, it is important to consider the desired features. Some questions to ask are:

What parameters do you want to measure?

Is it important to have current conditions or is a historical record enough?

How do you want to retrieve the data?

Environmental sensors

Generally, environmental sensors cost between $30 and $300. The most commonly used environmental sensors measure temperature, relative humidity, wind speed and direction, rainfall, leaf wetness, soil temperature, soil moisture in volumetric water content or soil matric potential and light. Of the two forms to measure soil moisture, most superintendents choose to measure soil volumetric water content. Light sensors come in three forms. It is crucial to understand the differences to avoid purchasing the wrong sensor. Foot-candle or lux meters measure light as the human eye sees it. Avoid these sensors, because plants see light differently than humans. Photosynthetic active radiation (PAR) sensors measure light available to the plant. Purchase a PAR sensor to analyze plant health and shade. A pyranometer measures total available light. This light measurement is used in the predicted evapotranspiration calculation. Environmental sensors can be operated manually to obtain current conditions or connected to a data logger to record information over time.

Data loggers

The combination of a data logger and environmental sensor makes a weather station. Data loggers under $100 typically have one or two built-in sensors, most often temperature and relative humidity sensors. The next step up in weather monitoring equipment is small data loggers, which run $200 and up. These have more flexibility, as external sensors are added based on a customer’s requirements. These data loggers typically only handle two to four sensors, but their small size allows them to be used in almost any location. For either of these systems, current conditions can only be obtained by going to the data logger, and data must be downloaded by plugging the data logger into a computer.

To start monitoring multiple parameters and obtain current conditions remotely, one needs to spend over $500 on a data logger. These units can handle more sensors, have greater computing power and can connect with remote communication devices. Full weather stations monitor all major parameters (temperature, relative humidity, rainfall, wind, light and evapotranspiration) and cost over $1,500.

Communications

Communication options with data loggers include direct connection, radio wireless, cellular and satellite. Direct connection offers the most reliability at the lowest cost, and it is the only option available with lower-end data loggers. Data loggers that are continuously connected are susceptible to lighting strikes. Therefore, direct connections are not recommended for stations left in the field. Radio wireless is a cost-effective (systems start at $500) method to avoid lightning problems. Radio wireless requires line of sight between the weather station and the base station. Connection via cellular or satellite is not susceptible to lightning and does not require line of site, but it comes with a higher price tag (around $1,500). A great feature of cellular and satellite connections is that the data is automatically uploaded to the Internet. Both direct connection and radio wireless can send data to the Internet, but they require additional technology.

The two lowest lines are sustained wind speed and wind gust. The next lowest line represents relative humidity. The upper two lines represent air temperature measurements from two different locations. A spreadsheet depicting data downloaded from a weather station. Data was collected on 15-minute intervals for PAR light, solar radiation, relative humidity, temperature, rainfall, wind direction, wind gust, wind speed and dew point. Images courtesy of Spectrum Technologies, Inc. Superintendents can use weather data to determine if recent rainfall produced conditions that are too wet for golf cart use.

Managing weather data

No matter where your data comes from, the most power from weather information comes from managing and analyzing it correctly. In order to do this, you need to use the software provided with a weather station or organize a spreadsheet. In either platform, you have the ability to analyze current conditions and create customized reports, such as disease prediction, growing degree calculation and predicted evapotranspiration calculation.

Air and soil temperature measurements can be used to explain problems, view fan performance, make management decisions and accrue a historical record. In Minnesota, for example, several superintendents have placed temperature sensors on golf greens for the winter. Just after snowmelt, they download the information from these sensors and review the data. The historical temperature information gives them an idea of what conditions the turfgrass experienced and what percent of damage they can expect. Another use for temperature information is the calculation of growing degree days (GDD). Research has shown that several insects and weeds emerge when a specific growing degree day is reached. Others have used surface temperature measurements to validate syringing practices to management.

Wind speed and direction information is most useful for planning spraying activities. Connecting wind sensors to a data logger provides a historical record that can be used to verify proper procedures were followed. Hand-held wind speed meters can be used to make on-the-move decisions about spraying.

Rainfall measurements can be used to determine irrigation needs, plan daily activities and determine whether golf carts can be used. At one Midwest golf course, the superintendent determined that any rainfall over 1 inch produced conditions that were too wet for golf cart use. After communicating this to clubhouse management, the superintendent eliminated any confusion about golf cart use.

Light is extremely important to turfgrass health. A PAR light sensor will provide information on whether a given location is receiving enough light at a point and time and whether that location receives enough light over a period of several days. Consultants can map light over an entire surface, for example, a golf green, to determine which trees are causing the most trouble. This information can be used to plan tree removal and trimming.

Wind speed and direction information is most useful for planning spraying activities. Photo by Rich Redles.

Soil moisture can be measured over time with an in-soil sensor or a mobile sensor. Either tool provides detailed information about current conditions. Through monitoring soil moisture levels, superintendents can target an optimal soil moisture level. This target is then used to plan irrigation events. Consultants can be brought in to map soil moisture across a site. This provides information on irrigation uniformity and irrigation head performance.

Combining data from several sensors allows the calculation of disease models and evapotranspiration. Researchers have published several disease models. All disease models incorporate various weather parameters, such as temperature, relative humidity and leaf wetness, to predict disease incidence. It is recommended that weather station software be used for disease prediction. If using a spreadsheet to manage data, extra care must be taken to input the correct parameters and factors to get an accurate disease prediction. The calculation of evapotranspiration using weather data requires temperature, relative humidity, solar radiation and wind speed. The predicted evapotranspiration calculated needs to be multiplied by a factor to obtain the correct predicted evapotranspiration. Contact your local university or extension office to determine the correct factor to use.

Weather data offers many opportunities to improve turfgrass management. Establishing on-site weather collection can provide information not available from other sources. In addition, the information is site-specific. Several factors must be considered when selecting the best technology for your course. It is important to consider what will be done with the information and how you want to collect the information.

Aaron Johnsen is an adjunct lecturer at the University of Wisconsin- River Falls and owner of Turf Intelligence LLC. At Turf Intelligence LLC, Aaron uses measurement technology to help turfgrass managers diagnose problems and develop maintenance plans. In addition, Aaron advises turfgrass managers on implementing measurement technology. You can contact him at turfintel@yahoo.com or www.turfintel.com.