Management zones are not always about cutting input costs; rather, they allow farmers to make informed decisions on the efficient use of inputs by placing them where they are needed in a field.
It begins with a change in mindset. Grid-based management remains popular across farm country and serves as the largest competitor to zone management. “Grid-based management works OK if you don’t have a lot of background information,” according to Brad Beutke, CropTech Precision Agriculture Technology Specialist. “But if you have the information, including yield history, calibrated yields maps, soil surveys, elevation maps or aerial imagery, then it’s worth the effort to take advantage of that valuable data.”
This is referred to as the smart-sampling approach. Instead of trying to randomize out variability with a super-imposed grid, zone management uses history to pave its own path. Regardless of where you are on the technology adoption curve, there are zone management techniques that can be beneficial.
Build your foundation of zone management based on soil characteristics. Soil variables such as texture, slope, depth, organic matter, fertility, cation exchange capacity (CEC), pH, drainage and density layers should be taken into account. In most cases, a free soil survey map obtained online provides a starting point to identify the variability of these factors in the field.
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. Essentially, 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 went down because an operator made a mistake with a planter versus an area of natural yield change in the field. But farmers and boots-on-the-ground agronomists do know those things.”
Start by looking for zones that repeat themselves year after year. It generally takes at least 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. “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 soon, hybrids—based off zone management systems.”
“Farmers want variable-rate population and nitrogen, and 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 variable-rate planting populations, 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 you’ll never change your ear counts,” Bauer says.
Using zone management is a journey—not a destination. The more effort you invest in verifying the management zones, the greater the payback to your bottom line.