If you think site-specific farming devices are toys for the rich, think again. Astute goals and sound planning can help you reap dividends.

Rick Oswald remembers his first dabbling with site-specific (precision) agriculture. He had taken a few soil samples that showed that his Missouri River bottom land needed 21/2 to 3 tons of lime/acre. Before he could put in his order, his fertilizer dealer acquired a grid soil sampling system with a global positioning system (GPS), and Oswald decided to give it a shot.

"The grid map showed that only half of my land needed lime and the other half didn't need any at all. But some areas needed 6 tons," Oswald says, who farms 1,700 acres of corn and soybeans in Langdon, MO. "The actual cost of liming was less than what the broadcast [over all acres] would have been."

That experience convinced Oswald that there was something to site-specific farming. He and several other panelists discussed the use of GPS-based tools at a conference called "Making Technology Pay," sponsored by Novartis.

The panelists agreed that the size of a farm and even a producer's computer/technology savvy do not determine whether he or she should buy a GPS service. The factors that are important are the type of manager the farmer is and the goals that have been set for the farm.

What GPS can do. According to Rob Stouffer, owner of Precision Insights, a precision ag consultancy in Lee's Summit, MO, GPS can be used in five major ways:

* Soil sampling. This is the basis for fertility management, where samples over grids, usually 21/2 to 5 acres in size, are taken and analyzed for composition, soil type, nutrient levels, conductivity and deficiencies.

* Variable rate technology. This allows variable rates of fertilizer and seed population to be used, depending on the soil type, nutrient needs, etc.

* Yield monitoring. This allows pinpoint mapping of yields. Hybrid/variety se-lection can be more precisely targeted with such data.

* Geo-referenced record keeping. This automatically records exact locations of different hybrids, populations, planting dates, yields, soil temperatures, etc. Thisis aided by a data-logging device on the planting tractor, as well as a yield monitor on the combine.

* Remote sensing. Although still in the development stage, satellite imagery using infrared or near-infrared technology can indicate stressed areas in a field, perhaps from weed pressure or disease. Solutions can be implemented while there is still time to correct the problem.

The value of GPS-based data is unveiled in the analysis that comes from the study and overlaying of the maps, called geographic information services (GIS), Stouffer says. For instance, yields can be compared with seed population or different hybrids, hybrids can be compared with nitrogen levels, and seed population can be compared with soil type. Multiple-year maps can be overlaid to show trends, and input/harvest data can be combined to produce profit maps.

The combinations are almost unlimited. The goal is not to produce lots of information but to maximize profits. Stouffer notes that sometimes it is a case of better managing costs, not just increasing yields.

Selecting a service. Producers making the dive into site-specific ag can buy the equipment and software and provide their own analysis, or they can select a service provider, often through a custom applicator, implement dealer, crop consultant or precision ag specialist.

Wally Riebesell, general manager of MO Valley Agri Service, Rock Port, MO, advises that, when shopping for a service, be sure to find out who is doing the lab analysis of the soil. Make sure the company is reputable and has experience with soil from your area.

In addition, find out what grid size the service uses. There is a huge difference between a 3-acre and a 41/2-acre grid size. When Riebesell first started, he used 31/3-acre grids but has since lowered that to a 21/2-acre size. "That gives us a few more samples in a field. For a field smaller than 20 acres, we'll do 1- or 11/2-acre grids," he says.

He strongly advises farmers to find out exactly how the data and analysis will be presented. Some services provide a useful agronomy book that conveniently stores all the maps, information and recommendations.

The maps produced by the software are vital, Riebesell says. Make sure you see samples. Do they include good reference points, such as barns, windmills, tile inlets, roads or ponds?

He also says to ask the service provider how the software makes its calculations. If there are abrupt changes in the maps, that means the liming applicator, for instance, will also make abrupt changes. Instead, he says, there should be a "feathering" effect.

"If a field shows X in one location, and 3X in the next, that means 2X is somewhere in-between. Our software makes 200 calculations in all directions from each point," he says. Stouffer thinks that one of the top criterion a producer should consider when shopping for a service is experience. At the bottom of the list is price.

He also says confidentiality and trust are major issues. Check the service provider's office to see if other people can view computer screens with maps and if analysis books and disks are lying around. These data should be as confidential as any financial records, and your service provider should treat them that way.

Stouffer also says that the service provider should have a "big picture approach" to precision ag. "If all they provide is grid sampling and variable rate fertilizer, eventually the producer will be disappointed," he says. Instead, make sure the service provider is also pursuing the analysis (GIS) end of precision ag so that hybrids can be selected and seed population recommended.

On your own. The do-it-yourselfer Oswald says that his main criteria in selecting a GPS-based package include easy-to-use software, upgrades and technical support from the software company. He started four years ago with a complete hardware/software package from Case IH. Several implement manufacturers, including John Deere and AGCO, also offer systems.

"My software is simple enough to operate. Anyone can do it," he claims.

The main pieces of equipment are a yield monitor, GPS receiver with differential correction, antenna and a powerful PC. Because of the map painting, Oswald advises that producers use at least a 266-MHz Pentium with a 2.5-gig hard drive, and a large video card. The yield monitor comes with a data card that can be plugged into a PC or laptop, allowing for the transfer of data to the software program.

Farmers also have the option of just installing a yield monitor with GPS receiver and handing the data card over to a crop consultant or service provider. The provider can then extract the data, analyze it, create the various maps and make the recommendations.

Costs of GPS. As with most new technology, there's nothing inexpensive about GPS/GIS. A yield monitor will run about $5,000, according to Riebesell, with the GPS receiver adding another $4,000. If a producer doesn't have a computer, those costs need to be tacked on. Oswald says that some package deals from implement manufacturers could run $6,000 to $8,000.

For the GPS service, expect to pay $6 to $9/acre for grid soil sampling, depending on your geographic area. If a specialist analyzes the data card, he or she could charge anywhere from $0.75 to $1.75/acre. A consultant may charge by the clock, in a range of $30 to $80/hr.

Although GPS may seem expensive, both Oswald and Riebesell are confident that the systems pay for themselves - sometimes in the first year. Oswald says that the best benefit he's received from using GPS is precision hybrid selection.

"Seed performance varies from farm to farm. I planted six varieties of soybeans, and there was a 15-bu. difference from the best to the worst," Oswald says. "If you figure beans at $6/bu., times 15 bu., times 800 acres, you can see the difference. It paid for itself the first year."

Riebesell says the key to making GPS/GIS work is how the farmers put it to use: "If they perceive it as a farming tool, then it's an asset. If they just want to print maps, then it's an expensive toy."