Farmers go high-tech to pinpoint fertilizer usage

Farmers are using computers and global positioning technology to pinpoint fertilizer applications that can boost profits while reducing water pollution.

Variable rate technology, which applies fertilizer in the precise amounts needed in specific field locations, “keeps down the farmer's cost and is good for the environment,” said Kenver Scott, ag technology manager at the Linn Co-op Oil Co. in Springville.

Precision agriculture, made possible by grid sampling and GPS technology, “will have a positive impact overall on the environment,” U.S. Secretary of Agriculture Tom Vilsack, a former Iowa governor, said.

Bill Northey, secretary of the Iowa Department of Agriculture and Land Stewardship, said the technology ensures that farmers don't over-apply phosphorus and potassium, reducing the likelihood of affecting water resources. Adapting the technology for nitrogen fertilizer, which is more problematic because of its volatility, is in its infancy, Northey said.

The process starts with a battery of soil tests conducted on a grid broken down into 2.5-acre units. Data showing fertility levels throughout a field are converted into a computerized map that, with guidance from global positioning system satellites, directs the application of the exact amount of fertilizer needed for optimal crop production, Scott said.

The fertilizer is applied by a half-tractor, half-truck rig called a “floater” in deference to its large flotation tires that enable it to traverse wet farm fields with minimal soil compaction. With its 90-foot boom and average speed of 12 mph, the floater can fertilize 1,000 acres a day.

“I think it saves money, but it also puts the fertilizer where it does the most good,” said Allen Platner, 70, of Marion, who has been using the technology for most of the decade on his 700-acre, central Linn County operation.

Curt Zingula, 58, of rural Marion and farming 1,460 acres in northeast Linn County, said the practice enables him to build the fertility of low-testing soils without overloading high-testing soils.

Zingula, who adopted the practice in 1999, said he appreciates the assurance that his fertilizer is being used by crops rather than washing off his fields.

Joe Meythaler, who fertilizes parts of his 2,000-acre Linn County farm with livestock manure, said he especially likes the system's ability to coordinate manure and commercial fertilizer usage.

“After eyeball application of manure, it tells me if I need to add commercial fertilizer and, if so, how much,” Meythaler, 50, said.

Variable rate technology research findings show “a clear value for environmentally friendly fertilizer application,” according to Antonio Mallorino, a soil fertility and nutrient management professor at Iowa State University in Ames.

“I feel it is very useful and feel every farmer should use it,” Mallorino said.

At least half of Iowa farmers have adopted the technology, he said.

The computer-equipped floaters apply about 70 percent of the phosphorus and potassium fertilizer used each year by Linn Co-op customers, Kenver Scott said.

“With fertilizer prices going up all the time, we think more farmers will adopt the technology,” he said.