The value of zone management goes beyond cutting input costs; it also allows farmers to effectively focus inputs and attention.
If you don’t have background information on a field, then grid-based management does the job, says Brad Beutke, who helps with the Farm Journal Test Plots and farms near Clinton, Ill. “But if you have yield history, calibrated yields maps, soil surveys, elevation maps or aerial imagery, for example, then it’s worth the effort to take advantage of the data.”
Instead of trying to randomize out variability with a super-imposed grid, zone management uses historical data and experience to pave a path. Regardless of where you are on the technology adoption curve, zone management is beneficial.
Build your foundation for zone management based on soil characteristics. Take into account soil variables such as texture, slope, depth, organic matter, fertility, cation exchange capacity (CEC), pH, drainage and density layers. In most cases, a free soil survey map found online provides a starting point to identify the variability of these factors.
Field management zones should be based on soil information and further refined using data from calibrated yield maps, normalized difference vegetation index (NDVI) maps, aerial imagery and remote sensing.
Use the data to manually draw zones on maps before moving to software. The manual process allows you to ground truth your zones.
“Be careful identifying man-made yield zones,” Beutke notes. “A computer doesn’t know the difference between a spot where yield dropped because an operator made a mistake with the planter versus a natural yield change. Farmers and agronomists with boots on the ground do know, though.”
Start by looking for zones that repeat themselves year after year. It generally takes three to five years of data collection to accurately establish zones. The result should be zones that range from three acres to seven acres. Zones can be merged back together in the future if variability doesn’t continue to present itself.
Once you create management zones, pull soil samples from each zone. The samples should show little variability within the zone, and the CEC, organic matter and fertility should be consistent across zones.
Well-defined and -verified management zones lay the groundwork for variable-rate technology (VRT). “Management zones are a farmer’s guide to variable-rate farming,” Beutke says. “You can manage all your prescriptions—dry fertilizer, nitrogen, plant population and hybrids—based off zone management systems.”
“Farmers want variable-rate population and nitrogen, but until management zones are established, there’s no good way for those to work,” adds Missy Bauer, Farm Journal Associate Field Agronomist.
When it comes to VRT, plant spacing must be perfect and higher ear counts demand uniformity. “If your plant spacing is a train wreck, don’t move forward with variable rate because you’ll change your populations, but it won’t impact your ear counts,” Bauer says.
Using zone management is a journey—not a destination. The more effort you invest in verifying management zones, the greater the payback to your bottom line.