Precision agriculture technology has been developed and used most extensively on Midwest farms, which tend to have very large, flat fields. Now Penn State researchers in agronomy and other disciplines are evaluating how the technology can be used most effectively on Pennsylvania farms, where fields are often small and hilly. The technology includes global positioning systems (GPS), which precisely locate field positions; geographic information systems (GIS), which manipulate and display geographic information as maps; yield monitors, which measure grain yields as a combine moves through a field; and variable rate applicators, which can apply inputs to targeted areas within a field.

Here's how precision agriculture works. A GPS receiver mounted on a combine monitors radio signals emitted by satellites orbiting the Earth. By comparing the time it takes to receive signals from different satellites, the receiver uses triangulation to determine its latitude and longitude. By using the GPS to precisely locate where soil samples, for example, are taken within a field, entering the results of soil tests into a GIS, then displaying those data on color-coded, computer-generated maps, farmers can see exactly how fertility, pH, and other factors vary across a field. They then can apply nutrients and other inputs as needed rather than averaged for the whole field.

Yield monitors in the combine add another dimension to precision agriculture. As a crop is harvested, sensors record the mass and moisture content of the grain, the combine's speed, and other variables. A small computer in the combine's cabin collects data and calculates and displays the yield as the combine moves through the field. By linking the yield monitor to a GPS receiver, farmers can record the exact location of the combine while the yield is being measured. When entered into a GIS, the results can be displayed on maps so farmers can identify how variations in field conditions, such as soil fertility, moisture, or the type of seed used, affected yields. This information can make it easier to plan for next year's growing season.

"Our farm has about 100 fields," says Lynn Hoffman, senior research associate in agronomy and manager of the College's agronomy research farm at Rock Springs. "The monitor provides a summary of the yields from each field, which helps us decide how much fertilizer to apply. But making decisions on a single year's data can be dangerous. Last year was very wet, so some of the drier parts of our fields had significantly higher yields than the traditionally more productive parts of the fields. That was due to the unusual weather, and if we had adjusted our soil fertility levels based on that year's yield readings, we would have been in trouble. You need to map yields for several years to get reliable data."

Lynn Hoffman, who manages the College's agronomy research farm, uses a GPS receiver mounted on the back of a pickup truck to determine the location of soil samples.

Precision agriculture technology could dramatically affect pest control strategies as well. For example, worldwide, potatoes require more pesticides than any other major food crop. In 1995, Penn State entomologists Shelby Fleischer and Zane Smilowitz and postdoctoral researcher Randall Weisz began mapping insect densities across potato fields, then analyzing these measurements with computers to estimate how insect populations change across the field over time and applying pesticides only where they would have the best effect. "If Colorado potato beetles, for instance, build up in hot spots in a field, growers could substantially reduce insecticide use by treating only the hot spots," Fleischer says.

The researchers took three pairs of fields, each consisting of two adjoining one-acre plots, and used conventional integrated pest management techniques on one, scouting for insects and treating an entire field when the pest populations became severe enough for economic loss. In the other field, they used their mapped-and-targeted strategy, or "precision IPM," as Fleischer calls it. "Traditional IPM programs tell us when to intervene," he says. "Precision IPM also tells us where to intervene, based on how populations move through a field over time. We found this approach reduced pesticide use by 40 to 80 percent over conventional IPM, which typically reduces pesticide applications by 10 to 40 percent over standard management practices."

In a related study, graduate student David Midgarden showed that precision IPM also reduced the development of insecticide resistance. He performed bioassays on Colorado potato beetle larvae before and after fields were treated using conventional or precision IPM practices. In fields treated conventionally, insecticide resistance consistently increased as the fields were sprayed. Resistance tended not to increase in fields where precision IPM was used, because susceptible populations were maintained within the field. "Precision IPM leaves unsprayed areas in the field, which serve as refuges for both susceptible insects and their natural enemies," Fleischer says.

To make precision IPM cost-effective, Fleischer and graduate student Paul Blom are using a backpack-based GPS that connects to a palm-sized computer. "There's potential for IPM scouts to visit a farm with a GPS unit and map insects in the field," he explains. "This could lower the cost of mapping, while enabling growers to limit their pesticide or biocontrol treatments to parts of fields where they'll be most effective."

Paul Blom, graduate student in entomology, uses a backpack-based global positioning system (GPS) receiver to precisely record the positions of insect pests in a potato field. By incorporating these data into maps, researchers hope to develop and integrated pest management system that helps growers know both when and where to treat insects in the fields.

Computers also have made it possible for agricultural service companies to deliver site-specific weather information, which can help growers improve insect and disease management as well as other production practices. SkyBit, Inc., of Boalsburg, which recently introduced such a service to producers, takes raw National Weather Service data, then uses computers and information technologies to develop customized weather forecasts, which can be tailored to each farmer's needs. "Our company provides these forecasts to growers across the country," says Joseph Russo, president of SkyBit. "We can produce two-day reports that forecast the weather for a single farm on an hourly basis." By entering this information into pest development models based on weather observations, SkyBit also can forecast when insect and disease problems will develop on individual farms. "Many IPM programs use weather data to determine when crops are likely to be threatened by various insects and diseases, and when insects are most likely to be controlled successfully," Russo says. "For instance, tufted apple bud moth is susceptible to most insecticides for only a brief period after the larvae hatch. By evaluating weather conditions at the farm level, SkyBit can help growers know exactly when the larvae are most likely to appear in their orchards."

Russo is working with Penn State plant pathologist James Travis, extension agent William Kleiner, and extension entomologist Carl Felland on a three-year study to evaluate SkyBit's weather data for apple orchard management. Twenty-five growers from 11 different counties receive customized weather and pest reports by either e-mail or fax each day of the growing season. "These reports let growers look ahead and know when the wind will die down, in what direction it will be blowing, and what the temperature will be at different times during the day," Felland says. "This information helps them plan when to scout for insects and when to treat pest and disease problems." After the first year of the project, growers reported that SkyBit's products boosted their confidence in managing several pests and enabled them to give spray operators more precise instructions on application timing.

While new technologies have enormous potential to help farmers, they need to think carefully before investing in a complete precision agriculture system, which can cost up to $20,000. "While these systems have become common in the Midwest, a lot of questions remain about their potential on farms in the Northeast, and some minor technical glitches need to be resolved," says agronomist Doug Beegle. "For example, GPS receivers don't always give accurate readings at the edges of fields. That's not very important in a 160-acre square plot, but edges might make up 25 percent of a long, narrow Pennsylvania field. We've also had problems with mountains blocking the GPS antenna's access to satellite signals. Once when I was using the combine, the GPS lost track of the satellites, and all of a sudden the readings said I was in the Atlantic Ocean, just off the coast of Argentina. Obviously, that's a problem if you're trying to get accurate information about your field. Just because the technology is on the market doesn't mean it's ready to be used yet. A lot of bugs still need to be worked out. Farmers would like to map yields and pinpoint trouble spots, and existing products can do that, but it's still very difficult. Companies need to make precision agriculture technology easy for farmers to use."

Eventually, Beegle believes, the technology will become more user-friendly and less expensive, and the technical problems will be solved. Meanwhile, says agronomist Greg Roth, yield monitors–which cost about $3,000–are the best way for Pennsylvania farmers to begin reaping the benefits of precision agriculture technology. "Yield monitors have proven to be accurate, and they can provide very valuable information about entire fields. They also can help growers evaluate products and practices. Farmers have to choose from a lot of different cultivars and other inputs, but often they don't have good data on their effectiveness. With yield monitors, farmers can easily conduct side-by-side field trials and confirm whether one product really outperforms another."

Faculty and staff referenced in this article are Douglas Beegle, professor of agronomy; Peter Bohn, senior project associate in agronomy; Dennis Calvin, associate professor of entomology; Carl Felland, research assistant in entomology; Shelby Fleischer, assistant professor of entomology; Lynn Hoffman, senior research associate in agronomy; Larry Jenkins, associate professor of agricultural economics; William Kleiner, extension agent in Adams County; Janis Pruss, manager, crop management program and affiliate instructor in agronomy; Gregory Roth, associate professor of agronomy; Gary Sheppard, extension agent in Westmoreland County; Zane Smilowitz, professor of entomology; James Travis, professor of plant pathology; and Laura Watts, extension agent in Cumberland County.

Research discussed in this article has been funded by the Pennsylvania Department of Agriculture and the Northeast IPM Special Grants Program.