Technology has arrived: Site-specific management
As a new father, I continually seek the advice of family, friends and experts on how to best raise my 8-month-old daughter. While their recommendations vary, they all agree on one piece of advice: "No two children are alike." Until recently, our recommendations for managing turf and the surrounding landscape have not been so "site" specific. For instance, we have commonly relied on general, broad-based recommendations in developing and employing nitrogen-fertilizer application programs. Now, a new technology called site-specific management (SSM) is available to help professionals manage their grounds on an as-needed basis. Also referred to as precision farming, precision agriculture, precision turf management, etc., SSM for grounds maintenance is the management of soil, plants and other resources according to localized conditions within a facility. In other words, SSM is a tool to help grounds managers identify and manage variability that exists on their site. We can best explain SSM for grounds maintenance by describing four basic technologies: global-positioning system (GPS), geographic-information system (GIS), sensing and variable-rate technology (VRT). Let's look at each.
Global-positioning system (GPS) GPS allows you to determine a precise location on earth. Initially developed by the U.S. Department of Defense as a military navigation system, GPS uses a constellation of more than 24 satellites orbiting earth. It works by having a receiver (either hand-held or attached to a utility vehicle or mower) that accepts radio signals from the satellites. Using the equation of velocity = distance/time, the receiver calculates distance using the known velocity of a radio wave and the time elapsed for a radio signal to travel from the satellite to the receiver. Because the exact position of each satellite is known at any given time, the receiver then uses geometry to calculate a longitude and latitude using the distance measurements from a series of satellites. Sound fairly simple? Well, not quite. Currently, the GPS satellites transmit signals on two frequencies. For national security reasons, civilian users cannot access a code for transmission of both frequencies. As a result, the GPS receiver calculates inaccurate positioning data. To achieve desired accuracy, civilians can use differential GPS (DGPS), which is a method requiring two GPS receivers. Using DGPS, the position of the GPS receiver in the field is calculated based on its reference to a base GPS receiver located on a point of a known position.
Obviously, knowing where you are is a key to SSM. GPS allows you to identify the location of turf areas, trees, irrigation heads, drainage lines and just about anything else that is important to your site. How accurate do you need to be? The answer to that question depends on how much money you want to spend. For as little as a few hundred dollars, GPS technology will place you within several yards of your precise location. Other GPS units provide accuracy to within inches but cost the user several thousands of dollars.
Geographic-information system (GIS) Now that you have the power to accurately determine the location of any object at your facility, the next question becomes how do you deal with all of these data? GIS comprises mapping software that supports the capture, management, manipulation, analysis, modeling and display of spatially referenced data. Using both GPS and GIS, you can produce highly detailed and accurate maps of your facility. GIS software allows you to create map layers corresponding to variables such as irrigation spacing, turfgrass species or disease incidence and then overlay other maps to analyze relationships among variables. GIS software also acts as a living historical file. You can view the history of an area at one time to track information such as pest movement, chemical application, soil-test data, irrigation records and drainage patterns. Some of the additional benefits of GPS/GIS technologies include tracking the location and monitoring the condition of maintenance equipment, site-specific recording and reporting of daily maintenance activities including scouting of pest activity and localized dry spots, and pre-programming application equipment to prevent application of chemicals onto environmentally sensitive areas. GIS software for grounds-maintenance applications is currently available for use alone or in conjunction with GPS. Furthermore, certain companies will develop GIS software that is specific for the needs of your facility.
Sensing Sensing becomes an important part of SSM when you consider the magnitude of variation that exists in nature. As an example, research conducted recently at Oklahoma State University found that nitrogen levels in wheat varied significantly between areas greater than 9 square feet. In other words, soil tests taken from areas larger than 9 square feet may not accurately describe the within-field variation in nitrogen. Let's say you decide to take soil samples every 9 square feet from a 160-acre site. Your bill for soil testing would be $7,744,000, assuming $10 per sample! It is easy to see that you must conduct accurate characterization of within-site variability with a sensing device that will allow collection of data on a much finer spatial resolution than is currently feasible with manual or laboratory procedures.
Sensing depends on the measurement of energy that an object reflects. You'll obtain the most valuable agronomic information from sensing by measuring electromagnetic radiation that is reflected by the plant or soil in the visible and near-infrared (non-visible) regions of the energy spectrum. Some in the field currently are using (or testing) ground-driven sensors to measure soil-organic-matter content, soil and plant moisture, soil and plant nutrient levels, and pest incidence. Remote sensing uses the same principles except that the units capture spectral data from an airplane or satellite. Sensors hold much promise for use in SSM because they provide quick, indirect, real-time measurements, finer spatial resolution, multiple functions and the potential for easy use in maintenance operations.
Variable-rate technology (VRT) Once you characterize variability within your site, the next step is to treat according to the site's specific needs. VRT was developed for the precise application of chemicals and plant propagules. Many manufacturers now are developing machinery to apply specific amounts of fertilizer, pesticides and seed to areas on an as-needed basis. At Oklahoma State University, researchers developed a sensor-based variable-rate system for liquid applications of nitrogen. Researchers mounted sensors on the front of the sprayer corresponding to the nozzle spray width. In the back of the sprayer, they located four nozzles (instead of only one) at each spacing, and they sized each nozzle according to a different application rate. As the sprayer crossed the field, the sensors optically detected the level of nitrogen in the plants and, in real time, the variable-rate applicator then added nitrogen at different rates depending on plant needs. Researchers now are developing other variable-rate applicators for application of both liquid and dry materials.
SSM: The future of grounds maintenance SSM is a new approach to manage grounds facilities on a smaller scale (inches to feet) compared to conventional practices (thousands of square feet to acres). This technology, like many other new technologies, is expensive. Nevertheless, researchers and manufacturers expect costs to decline with increased use. The advantages of SSM include improved estimation of variability within the site, optimization of inputs to the landscape, improved profitability to the operation and the reduced threat of environmental contamination from overuse of chemicals. SSM uses GPS for positioning, GIS for spatial mapping and analysis, sensing for efficient plant management, and VRT for precise application of chemicals and plant material. So remember, no two areas of your facility are alike--just like no two children are alike.
Dr. James H. Baird is assistant professor of Turfgrass Physiology in the Department of Crop and Soil Sciences at Michigan State University (East Lansing, Mich.).
The author wishes to acknowledge the contributions of Beau J. McSparin and Geoffrey J. Rinehart, graduate assistants in the Department of Crop and Soil Sciences at Michigan State University, in preparing this article.
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