You’re only as strong as your weakest link
The saying, "You’re only as strong as your weakest link," rings true with zone management. When implementing zone management, decisions have to be based on a firm foundation and recognition of the factors you can and can’t change.
"Many of a farmer’s agronomic decisions and limiting factors are interlinked," says Farm Journal Associate Field Agronomist Missy Bauer. "For example, a farmer might have a bigger nitrogen problem because of a low pH. Then that farmer really has a nitrogen efficiency problem."
To increase yields, farmers have to respect what they can’t change and act on what they can. When working with farmers to execute zone management, Bauer says to first focus on the soil.
"The foundation is to understand soil characteristics, including CEC [cation exchange capacity] and organic matter. You can’t change soil type, but you can manage it for maximum yields," she says. "Too often, farmers fault the soil and label it as poor yielding. But it’s worth a closer look."
A soil test will reveal the weak link in a field’s fertility. To underpin zone management, Bauer encourages farmers to handle fertility by zones, not grid.
"We can fix issues with pH, potash, phosphorus and the base fertility," Bauer explains. "We can’t measure any other variability until those issues are corrected. Some soils have to be continually monitored."
Uniform treatment of fields that need to be managed differently by zone will cause farmers to pause.
"For our area of the eastern Corn Belt, pH is the most common characteristic that exemplifies zone management. We have acid soils that range from 1.5% to 3.5% organic matter in the same field," Bauer explains. "Over time with uniform lime application, we’ve developed hot spots in the field. With zone management and variable-rate application, we are able to correct and shrink those areas."
A surprising aspect of zone management is that a historically low-yielding area might exist only because it was treated like a low-yielding area.
"When farmers look at yield maps and see reoccurring red zones, they shouldn’t just say it’s bad soil," Bauer says. "There are ways to manage around the weak links we can’t change."
Water management is one aspect that farmers might be able to manage around. Another example is a farm with high pH and high water-holding capacities that leave corn with wet feet, explains Farm Journal Field Agronomist Ken Ferrie.
"You may be able to drain the zone but then select for a hybrid that can handle the high pH," he says.
After a couple of years of his own data, Le Roy, Ill., farmer Mike McLaughlin is more confident in hybrid placement.
Hybrid selection. The No. 1 factor farmers can change is hybrid and variety selection.
"If you have weak links with your soils, you may not be able to support the racehorse hybrid and may need to plant something more defensive," Bauer says. "Same with lighter soils and low pH—you can select a hybrid to handle that environment."
When reviewing yield maps and defining and redefining zones, Ferrie says it’s key to select the right hybrid for the right spot and not to pick a hybrid for the wrong reason.
"With the yield maps we analyze, the common weak link is not picking the right hybrid," Ferrie says. "We can see where we put two hybrids in a field and one is superior by 50 bu."
Ferrie says the ball is in the farmer’s court to pick the best hybrid, with help from their seed rep and combing through all available data. Then it’s time for boots-on-the-ground experience.
"I know a farmer is on track when he tells me why specific hybrids are placed in certain fields," he says.
When selecting hybrids, knowing the weak links helps Le Roy, Ill., farmer Mike McLaughlin make decisions.
"We have areas in fields that don’t drain well, and we have really light ground," McLaughlin says. "Those extremes are what we select for; we place hybrids that can have wet feet on the wet ground then place true flex-ear hybrids on the lighter ground because we’ll decrease the population at planting."
McLaughlin makes it a priority to evaluate several potential hybrids each season by planting no more than one-fifth of his ground to a single variety.
"That’s my comfort level, and overall, I’ll pick four or more hybrids that can be planted to a majority of our acres," he says.
On-farm trials, yield maps and in-field evaluations have helped build his confidence in choosing hybrids.
"I’ll test a new hybrid for two years and get the opinions and experiences of guys I trust," McLaughlin says. "But I don’t count out a hybrid based on one year and just one field. It’s a process that takes time but can pay off."
Field trials for hybrid selection are worth your time.
"We learn so much more when field trials are on our own farm," Ferrie says. "You can’t spend too much time analyzing hybrids and how they responded in your management zones."
He notes it is important to use calibrated yield monitors because yield maps are only as valuable as the calibration. Also, when doing hybrid evaluations, each hybrid should be in separate loads and be backed up with scale tickets.
Before McLaughlin adopted variable-rate population, he used split-planter trials and manually changed populations. Both practices were extremely valuable and took little financial investment to execute.
Using a split planter, McLaughlin says you can see where hybrids yield the same and where they’re different.
"It may not be the wrong hybrid for your farm operation, but it could be for that field and that management zone," Ferrie says. "If you don’t start studying those maps based on hybrid response to management, you’ll never have your own data to be comfortable," he adds.
Armed with personal data, farmers can make decisions in new ways. When combining factors that can and can’t be directly changed, knowing as much as possible will build farmers’ confidence in how they use zone management to farm.
"For example, sands and heavy clays can exist in the same field," Ferrie says. "Farmers have to decide to farm a field for what it is. When it comes to genetics, choose for the majority but respect the minority."
The payoff in on-farm field trials extends to nitrogen management.
"This past year, especially, if a farmer missed the window with their nitrogen application, 30 lb. of nitrogen made a $100 difference in the return on investment," Ferrie says.
With uniform sidedress rates, a farmer might not know the yield potential that was possible.
Ferrie recommends that farmers skip a pass in the field, as well as double-up rates in a pass to learn from that check strip.
"You can have a tendency to second-guess yourself in zone management," McLaughlin says. "Especially at sidedress, when the zone management dictates a low rate of nitrogen, it can cause discomfort."
Despite his natural reaction, McLaughlin says he can steady himself in knowing that his application is based on personal data.
"You take the chances where you think you have the best shot," he says. "If you have the basics in line, they can take you a long way. For example, we prioritize putting starter fertilizer on the acres where we know it can have the most positive impact—where there are low phosphorus levels in our soil tests and on corn-on-corn ground."
There are numerous weak links that can affect your final yield. Managing them in order will help you eliminate them one at a time. Each step stresses the importance of accurate data collection, analysis and ground-truthing.
"Weed control is one example," Ferrie notes. "If there’s a weed escape that appears as a red spot on the yield map, you need to be able to answer not only what the red spot is but what caused it."
The same applies to all pest management—insects and diseases—as well as other yield-robbers.
Scout it out. Zone management requires intense observations through the growing season, scouting and yield mapping. When zones are being built and refined, it takes repeatable data to confirm or dispute those decisions.
"Without overlaying your data, you could be making mistakes you don’t realize," Ferrie says. "You can’t speculate on one layer of data to change your whole management style. Instead, it takes all of the information to build strength in your zones."
It’s important to not just answer where yield is being lost, but come up with why through ground-truthing. In fact, this has lead Ferrie to want to change his terminology from "ground-truthing" to "efficient scouting."
"When we ground-truth something, farmers should take the opportunity to know the stand count, evaluate ear size and observe plant uniformity," Ferrie says. "With today’s aerial imaging tools, farmers should do the diagnostic work—march in the poor area and collect as much info as possible. Then go to the good area. Figure out when in the season the problem took place."
Today’s technologies help provide a new level of understanding the weak links in a field—but they don’t answer every question.
McLaughlin credits his yield maps with being an excellent teaching tool, but they have limits. "When we sit down with our yield maps, sometimes our yield-limiting factor is obvious. Sometimes it’s not," he says.
In-season mapping can also help fill in some of those blanks.
"We’re able to build management zones; pull soil tests; use in-season scouting aides such as thermal and NDVI maps; overlay with calibrated yield maps; and then swap notes on what was seen in the field. That really builds a farmer’s confidence in what he can and can’t control," Ferrie says.
Even with all of the layers of information, Ferrie says farmers should not get overly frustrated when the answers to some problems aren’t easily found.
"Too many farmers with thermal imagery, for instance, saw a spot on the thermal map, went out to the field to scout and when they got there, they scratched their head. It may not be obvious," he says.
Bauer agrees. Zone management is a process of continual improvement and demands ground-truthing.
"To me, that’s the only way you’ll know for sure you have zones in the right spot," she says. "Because you don’t know the answers unless you go out and find them."
You can e-mail Margy Eckelkamp at firstname.lastname@example.org.
To learn more about how to get started with zone management and see more data from real-life case studies, visit www.agweb.com/InTheZone
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.