Walking out in the field and ground-truthing zone management data and decisions is key, says Farm Journal Field Agronomist Ken Ferrie (right).
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."
- January 2014