Walk through your crop to spot variable conditions within management zones
With the crop in the ground and summer in full swing, now is the best time to fine-tune your management zones using a multipronged approach, says Isaac Ferrie, Farm Journal College presenter.
First, gather and evaluate in-season imagery to define differences within the zones. The more imagery, whether normalized difference vegetation index (NDVI) or thermal, the stronger the data points will be when layering. Second, walk fields to spot variable conditions and evaluate what’s happening within zones. Take note of any visible differences, including nutrient deficiencies, spots that are too wet or too dry, or corn that is visibly larger or smaller within areas of the field, Ferrie says. This information is vital to make sure data matches what’s in the field.
Pair soil types and yield results with out-of-season agronomic measures such as soil analysis, tissue analysis and electroconductivity mapping.
Thermal imaging captures measurements every 10 days to closely monitor crop changes. “With any aerial service, you might ask for a high-resolution photo to be taken at the same time to ensure there weren’t obstructions from clouds,” Ferrie cautions. “Even with all these maps, farmers need to put their boots on the ground. Look at each layer independently, separate each crop and look at each year differently—the in-field experience is key.”
Common issues that show up on maps and need ground-truthing include water management and soil health.
“In a dry year like 2012, problem areas inside the same soil texture ranged from an acre to the size of a house,” Ferrie says. “We looked below ground in those pockets and found perched water tables. That indicates a water supply problem, which has to be taken into consideration when we make the population map.”
To help digest the massive amounts of information, review zone management layers one at a time.
“Farmers are in the driver’s seat to verify zones,” says Farm Journal Associate Field Agronomist Missy Bauer. “We have yet to find a computer that can replace a farmer’s in-field knowledge. To achieve really good management zones, layer multiple sources of information, including human experience.”
Ferrie likens managing zones to writing an open book. “We learn a little more each year,” he says. “The lesson along the way is that we don’t have all of the answers.”
Calibrated yield maps can reveal new management zones. By using other layers of data and ground-truthing, several zones in the field above were further divided (as indicated by the white circles) to create new zones.