Farmers in Wisconsin may soon have a powerful new tool to help them make decisions about fertilizer that increase their yields and control runoff, thanks to University of Wisconsin-Madison researchers who are studying how to maximize information from agricultural modeling systems.

Agricultural modeling systems analyze data about weather, landscape, crops and management techniques to produce maps that predict soil water content, grain moisture and the effects of compaction on yield. Farmers can use these maps to help them make decisions about how much fertilizer to spread, for example.

"Agricultural models are most important in helping to make management decisions," Molling says. "Yield is a measure of the success or failure of those decisions."

Molling, along with John Norman, Cristine Morgan and Birl Lowery of the College of Agricultural and Life Science’s soil science department, wanted to determine how much data are necessary to create models that would give the farmer accurate and useful information. The most costly and time-consuming data involve charting the characteristics of the land, so they studied how effective different levels of data were in predicting the actual yield of a test field.

For the first level of information, the researchers used data from a USDA soil survey and a USGS topographic map. For the second level, they added information about past yield, and used global positioning system devices to map the elevation of the field. For the third level, they used specialized equipment to get information about the soil, including the thickness and locations of the soil horizons and how much water it could hold.

"We found two different levels of information that will be useful to farmers," said Molling. "The first is using yield data to get the water-holding capacity of the soil and combining that with a topographic survey. This is inexpensive, because most of the data already exists, and it’s a good introduction to using modeling."

The second level of information is more expensive, but it provides a higher level of information, according to Molling. "A farmer would hire someone with the proper equipment to analyze the structural characteristics of the soil and survey the field with a global positioning system. It’s more expensive, but it will give the farmer useful information — especially for land that he or she has not farmed before."

The modeling system tracks the movement of water across and through the soil, and lets a farmer see how changing management techniques, such as no-till versus chisel plow, affects fertilizer runoff. "Chances are that farmers can reduce their costs by using only as much fertilizer as the crop needs," Molling says. "And there are more and more regulations about fertilizer use, controlling runoff and spreading manure."

Molling knows of at least one company in Wisconsin that is trying to build enough equipment and knowledge to offer this new service to farmers, and she predicts other companies will follow suit. "As farmers learn about these techniques, they start to ask around for dealers," she says. "When the dealers hear about the demand, they then become interested in offering the service."

The researchers would now like to partner with a company to create easy-to-use, point-and-click software. "Entering the data into the system is the biggest problem right now, so we want to work on making it more user-friendly," Molling explains.