How to Navigate Zone Management

January 24, 2014 08:06 PM
How to Navigate Zone Management

How to navigate zone management decisions to realize the benefits of variable-rate technology over time

Editor's Note: This article is part of the Farm Journal multimedia series, which is designed to help improve bottom lines by maximizing yields, minimizing inputs and improving stewardship. Use this as your business guide to understand and implement zone management and the tools that make it possible.

Every risk has its reward. With zone management, the reward is higher yields and profitability. Farmers who want to vary inputs such as seed and nitrogen have to first get a handle on managing the zones in their fields. Farm Journal Field Agronomists Ken Ferrie and Missy Bauer encourage farmers to be students of their soils to minimize the risks associated with implementing variable-rate technology (VRT).

"When farmers establish solid fundamentals, it eliminates the surprises," Bauer says. "Understanding soil characteristics will help farmers weigh the risk factors involved with changing inputs by zones."

Weston Wiler, who farms near Hillsdale, Mich., spent five to six years reviewing soil data and refining zones before moving forward with VRT population and nitrogen.

"Zone management gives you the confidence that you’re putting inputs where they’re needed in the soil, and you’re not spending money you don’t need to," Wiler says.

The decision to vary population and nitrogen should be grounded in the fundamentals, but the risk factors for the two practices are different.

"Population rates are based on water-holding capacity. Soils that have higher organic matter and cation exchange capacity (CEC) will support higher populations," Bauer explains.

Before adjusting populations based on the zone, Bauer stresses the importance of farmers knowing how effective they are at their current populations.

"Farmers must know their ear count. Increasing population without knowing that ear count also
increased will not accomplish the goal," she says. "Compare planted population to ear count ratios. The thresholds should be no more than a 2,000 difference in corn-on-corn or 1,200 in corn-after-soybeans."

Bauer also advises farmers to evaluate how ear tips fill and understand if the hybrid has a fixed or flex ear.

"When working with farmers on VRT populations, they get frustrated in making yield advances when they didn’t first understand ear count, uniform emergence and planter performance," Bauer says.

A struggle that Ferrie has encountered is farmer opposition to dialing back population rates.
"There’s been tremendous resistance to VRT at lower populations," Ferrie says. "Farmers have been eager to push population on heavy soils, but they haven’t expected to pull back on lighter soils. It’s surprising how much yield can be gained by lowering populations on lighter soils. "
When planting a range of populations, Ferrie says it’s important to calibrate planters. Confirm performance in the field, particularly with finger pickup meters.

There’s more at stake. After working with dozens of farmers, Bauer says that there is more risk in VRT nitrogen because there is more yield potential to be lost.

"Nitrogen is very complex. The risk of getting your nitrogen rate wrong is potentially a big penalty," Bauer says.

In higher yielding areas, farmers often think the nitrogen rate should increase, but that isn’t always the case. Production practices with zone management might be opposite of what farmers think or have been doing.

"Those higher quality soils can mineralize nitrogen more efficiently," Bauer explains. "So it’s not just a simple equation of applying pounds of nitrogen per bushel of expected yield. The first risk farmers need to take is to change their mindset and challenge their traditional way of thinking."

To learn how your management zones respond to nitrogen, Bauer advises farmers to have plots in their own fields. Run different rates across all management zones, even at straight rates, to learn how soils will respond to nitrogen, she says.

"For example, take the average rate today and two rates higher and two rates lower. This helps establish a bell curve—what’s too low and what’s too high. That’s where I start and then look at soil characteristics within that," Bauer explains.

Management zones also need to be analyzed for the risk of nitrogen loss through volatilization, denitrification and/or leaching.

"Sandier, elevated soils with lower CEC and organic matter have a lower ability to supply nitrogen," Ferrie says. "But these soils usually have lower infiltration rates. During heavy rain events, water tends to run off instead of soaking in, which decreases the risk for nitrogen loss through leaching."

Conversely, low-lying soils with high water-holding capacity might stay saturated for days, so there is a higher risk of denitrification.

"In a nitrogen-friendly year, the lower-lying, high organic matter soils tend to yield more with less nitrogen applied than the lighter soils," Ferrie says. "Whereas in a high nitrogen-loss year, the lower-lying soils might run out of nitrogen quicker."

Visual appearance, tissue testing, nitrate testing, NDVI maps and other tools can help farmers analyze how their nitrogen program is satisfying the crop’s need.

Interlocked goals. Using VRT with population and nitrogen can’t be managed independently of one another.

"We can push yield by increasing population in heavier soils and decrease population in lighter soils, but it must be married with nitrogen rates," Ferrie says. "If you push population and under-support nitrogen, you could go backward. On lighter soils at lower populations, nitrogen rates might need to be pushed because the poor soils need higher rates applied."

That’s why Ferrie emphasizes that it is important for farmers to use all available zone management tools and conduct their own on-farm trials to confirm how zones respond to their management practices. By doing so, farmers can establish parameters for making a decision on when and by how much to vary inputs.

"The trials will give you a comfort level in how you implement zone management and VRT," Ferrie says.

From year to year, farmers can use what they learn to adjust the parameters for making changes. It’s key to remember that zone management is an ongoing effort.

"You can’t assign a time limit," says Ferrie. "And you always have to factor in the seasonal weather patterns."

When farmers sit down to build and refine zones at the end of a season, it’s important to review the data with the year’s weather patterns in mind. Ferrie advocates that farmers should use the past four, five or even more years to analyze production results in a variety of weather scenarios. 

A Decade of Farming in the Zone

weston wiler

Weston Wiler

One of Weston Wiler’s fields can have sand, gravel and clay, all in a 100-yard area. He jokes that he’s the poster child for zone management—a practice he says doesn’t come with overnight results.

"Over time, zone management gets better and better because you keep tweaking the zones and tightening your management. Five or six years into it, you’re really dialing it in," says Wiler, who farms in south-central Michigan.

Wiler, a first-generation farmer, teamed up with Farm Journal Field Agronomist Missy Bauer 10 years ago to implement zone management. His first step was to manage zones by soil type.
"In the past three or four years, we’ve been variable-rate seeding in the zones and doing the same with nitrogen sidedress applications," he adds.

While input costs have risen, Wiler has diligently worked to not waste any fertilizer. He says he uses about the same amount of fertilizer overall, but it gets applied where it’s needed.

As technology improves, so does zone management. Before the widespread use of GPS, zone management wasn’t possible. To tweak zones, he overlays yield maps with NDVI maps for an in-season perspective of how the zones are responding to his management.

"Don’t be afraid of it," he says. "Jump in and try not to be on the bleeding edge of technology, but maybe the leading edge."

For more of Wiler’s story, watch "AgDay" in mid-February. —Tyne Morgan

More to Learn

Tune into "U.S. Farm Report" on Feb. 15 and "AgDay" on Feb. 17 to 19 as Tyne Morgan presents the "Farming in the Zone" series. Hear from both a rookie and veteran farmer on why zone management is essential to taking their farming operation to the next level.

You can e-mail Margy Eckelkamp at

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