MANKATO, Minn. —Northfield area farmer Sam Peterson worked as an applicator for his local farm co-op right out of school. He was driving the crop sprayer applying the nitrogen to area farm fields. And that got him interested in split rate applications and how that could benefit their farm.

At that time, Peterson was already a member of the Minnesota Corn Growers Association. That’s why he was knowledgeable about the MCGA’s Innovation Grant Program. Now in its fourth year, the program is funded through the corn check-off and assists farmers with conservation-minded research projects.

Peterson understood variable rate applications of nitrogen increases nitrogen efficiency, crop yields, net profit and decreasing nitrogen loss. But he didn’t yet know what split rate applications would work on Peterson Farms. So he applied to be a participant in the Innovation Grant Program — one of 12 projects across the state.

At the recent MN Ag Expo, which took place in Mankato, Minn. Jan. 22-23, Peterson displayed charts and data showing three years of comparison studies.

“I was motivated to find out if variable rate nitrogen applications would generate positive returns on our farm, our soils,” said Peterson. He’s aware of the negative press farmers sometimes get for nitrogen contamination in stream and rivers. “So if VRN (variable nitrogen rate) shows us how we can ratchet down our N apps, decrease nitrogen runoff and boost yields in the process, that’s a win/win situation.”

Peterson is an ag economics graduate of the University of Minnesota. “My project compares three different variable rates of nitrogen compared to a flat-rate check. We’re comparing the economic return of each of these programs to see if they really are paying off.”

And what has he found out? “So far I’ve found each program generates different results. We had the same winner the first two years, but a new winner last year. It showed that all were kind of neck and neck. They each have a different way of producing results … and so far, there isn’t a single best way to do nitrogen apps on our farm fields.”

Nitrogen rates were 100 pounds flat rate anhydrous before corn planting; then side dress apps of urea in mid to late June in the 80 to 100-pound rate. This was corn on corn so thus the higher N rates. “Usually our farm does two years corn, one year soybeans; but these trials were always on second-year corn.”

So are farmers guilty of over fertilizing their corn crops? Peterson would say ‘yes’ in past years. “But recently, we’ve been driving down our pounds of nitrogen per bushel — maybe to the extent that we have under applied and limited our yields the last few years. We’re trying to find a happy medium and we think this split rate applications is showing us how,” he said.

Differences in soil type obviously can impact results and that too is part of Peterson’s analyses. “So we’re taking soil cores and testing for nitrates in the soil; also tissue samples to see how much nitrogen is actually in the plant. At this stage I can’t say which is the right procedure. It depends on your farming practices such as manure applications and how much pre-plant N you apply.”

The Peterson farm land has a history of hog manure applications; plus they buy quite a lot of dairy cow manure and turkey litter also.

He said their current cost per bushel for corn production is around $3.65. They averaged 140 bushel on that June 2 planting last season. The rest of the corn planted earlier averaged around 200 bushels per acre for 2019. “An average yield for us is around 210 bushels,” Peterson said. “Last year was not the best corn growing season.”

Peterson Farms plant 30-inch rows with 34,000-35,000 plants per acre. All acres are variable rate planted, so both corn populations and nitrogen apps are adjusted on the go. “Anymore, our combine monitor pretty much tells us how to farm,” summed up Peterson.  

For more information, contact Peterson at (507) 649-1582 or via email at