Corn+Soybean Digest
Sample SIS maps show four of 65 data layers that help analyze a soilrsquos productivity and the potential for improvement

Sample SIS maps show four of 65 data layers that help analyze a soil’s productivity and the potential for improvement.

Deep soil data helps boost productivity

Think Different Woodrill Farms is analyzing soils to a 4-foot depth to better understand their productive potential. Already, this has provided new insights to: Adopt an innovative in-field variable tillage program Refine variable-rate corn seeding rates Update variable-rate nitrogen plans

As Woodrill Farms looks for ways to boost productivity, it is taking a deep-down look at soils to help drive decisions it hopes will help it maintain or boost its current year-over-year trend-line average corn yield increase.

Unlike in the U.S., Woodrill, based in Guelph, Ontario, doesn’t have detailed soil surveys as a starting point for making management decisions, says Dan Breckon, a Woodrill agronomist.

“A lot of decisions we make are based on our understanding of soils, and we realized we needed to know more,” says Breckon.

So Woodrill decided to try out Trimble’s Soil Information System (SIS), which analyzes soil’s physical and chemical properties down to four feet – providing far more detail than is available from traditional soil surveys. SIS uses advanced sensors, soil coring and data analysis to produce high-resolution soil maps that describe soil properties with more than 60 data layers ranging from soil texture and chemistry to hydrology. It is gradually being introduced in the Corn Belt after having been used primarily in high-value specialty crops in the past.

After evaluating soil profile reports from three hilly fields ranging in size from 70 to 100 acres, Woodrill already has management changes underway.

First up: an innovative tillage program begun this fall that varies tillage within a field. And in the spring, they will be refining their approach to variable-rate seeding and fertility applications.

“We wanted to better understand management zones for variable-rate seeding and soil fertility and will be making changes in 2016,” says Breckon.

The Soil Information System process

Woodrill kicked off its SIS trial in 2014 when it hired Premier Equipment, a John Deere and Trimble dealer, to evaluate two fields. It added another field in 2015. All three fields will be rotated to corn in 2016, providing the first opportunity for Woodrill to implement what they have learned in the input-intensive crop.

The SIS evaluation begins by developing a high-resolution topography map and an electromagnetic conductivity survey to identify variability patterns. Based on these patterns, selective areas are probed with a geophysical penetrometer to measure compaction, texture, water-holding capacity and other factors down to 4 feet. After analyzing penetrometer, topography and conductivity data, SIS software targets locations for a final round of 4-foot probes to test soils for nutrients.

The end result is 65 layers of data that can identify productive potential and what steps could be taken to improve it, says Devon Liss, SIS product manager. “It can show you how intensively you can manage a soil to improve productivity based on the entire soil profile, not just what you see on the surface,” he says.

“It gives you an opportunity to look at what really is restricting crop performance,” adds Greg Kitching, a Premier Equipment precision ag specialist. “Knowing what is going on below the top 6 inches allows you to create more detailed management zones.”

 

Fine-tuning variable rates

Breckon says the SIS data opened his eyes to refinements in the variable-rate seeding and fertility programs.

Elevation, electromagnetic conductivity and topsoil profiles are proving useful to better understand management zones for variable-rate seeding, he says. “In our area, topographic variability within a field has a good correlation with yield,” he says. “High-resolution elevations show more precisely where yield stratification is and helps us identify the top and bottom 20% of our yield zones.”

Understanding the lay of the land and topsoil depths and soil properties in minute detail likely will alter variable-rate nitrogen prescriptions, he adds. “Nitrogen tends to flow from our hills to our deeper soil toward the bottom of hillsides,” he says. “These soils also have higher organic matter. So our deeper soils may get less nitrogen than they have in the past.”

The same factors have helped Woodrill fine-tune its variable tillage program.

“Areas in the fields that are highly prone to erosion with shallow soils will be in continuous no-till from now on,” Breckon says. Heavier, deeper and less-erosive soils were tilled this fall with a Glencoe Soil Saver outfitted with 12-inch sweeps and 4-inch twisted shovels to leave 30% residue cover.

Breckon wrote a simple tillage prescription – green means “go,” red means “no” – to prompt manual raising and lowering of the tillage rig from the tractor monitor. “We have worked with variable tillage before, but never on farms that are this variable,” he says. “There are more tilled and untilled areas in these fields. We didn’t have the information available to set the boundaries before.”

Learning costs

An SIS analysis can cost $20-40/acre (U.S.) in row crops, but can vary based on crop type, mapping resolution, grower objectives and reseller offering, according to Trimble.

This is a significant investment, but worth it considering the value of the information, says Breckon. “Our strategy is to go at it slowly, picking a couple of our most variable farms every year,” he says. “If you tried to do it all at once across an operation, the learning curve would be too fast in terms of what you could implement.”

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