That big house looks really nice, but what about that sandy hillside it’s built on? Likewise, increased accuracy is bringing big, new possibilities in varying seed population and variety, but is your big data firm enough to support those decisions?

Shannon Gomes, a soil scientist and crop consultant, helped map Iowa soils in the 80s before GPS was used, so he understands the inherent resolution problems with those early maps. He now operates Cedar Basin Crop Consulting near Decorah, Iowa—

“Most of the soil surveys were completed in Iowa way before there was GPS,” he explained. “Each aerial photo we used showed eight sections of land and each section was four inches by four inches.” So, he said, when you get right down to it, foundational soil map data in Iowa may be only 60 to 80 percent accurate.

“Lines now are found to be 50 to 200 feet off,” he said. From that resolution point—four inches equals one mile—Gomes has been steadily gaining better and better resolution as an early adopter of precision tools.

“I’ve invested in a lot of different hardware. I’ve got a pretty nice size pile of junk in the corner over there …” laughed Shannon. “On the bleeding edge, I think.”

Gomes works with farmers directly, providing soil testing, maps, hybrid recommendations and plant health prescriptions for corn and soybeans.

He provides prescriptions to his growers. Once decisions are made, Cedar Basin exports a SHAPE file to a dealer to drive a controller, whether Ag Leader, John Deere or another one. With fellow consultant Frank Moore, he also offers EC mapping and more accurate soil testing with the AutoProbe through Soil Investigative Services ( His life to date has been about understanding soils and field variability.

Gomes has used both Veris EC (electroconductivity) and the Geonics EM 38 (electromagnetics) to help build solid data. He likes both machines, but currently uses the EM 38 because of its ability to take accurate readings from eight inches above the soil. He pulls the unit with an ATV and uses the EM maps to make his soil testing smarter.

“I’m able to go through the field even when there is a crop in the ground,” he explained. “It offers me a wider window to get the work done.”

Both units measure the soil’s ability to conduct current. Conductivity levels help identify patterns in organic matter, cation exchange capacity (CEC), depth to claypan, water-holding capacity and salinity. The unit picks up data continuously as it moves through the field. It’s then mapped with ARCview. A recent EM map he did of a field mapped with a Veris unit 12 years ago showed consistency in the methods and little change in the field during that time.

With increasing attention being placed on varying plant populations and hybrids in the field, Gomes says money could be wasted unless you are starting with something solid.

“These maps, I think, are going to be useful when you are looking to vary plant population—waterholding capacity is going to be a good indicator for increasing population,” he said. “The foundational data is very important in this case. Otherwise, what are you basing your changes upon?”

Gomes sees many limitations to grid sampling and is concerned that some farmers and retailers may be making their decisions on samples pulled in a very haphazard manner and is “not a fan of grid sampling.”

So, what will make your data foundation more solid?

“It’s a numbers game,” he said. “Being accurate takes more samples. It takes time.”