Field soil type and conditions are not uniform across every acre. Different soil, topography and pH means that, to achieve maximum yield, you’ll need to cater to each acre differently.
“Management zones should be in the 3- to 7-acre range with respect to soil types,” says Brad Beutke, who works with CropTech and is a presenter at Farm Journal Corn College. “It has to be a man-made process—it can’t be computer-generated.”
It can take time to truly fine-tune your field zones, but he suggests you start with soil maps. Check websoilsurvey.sc.egov.usda.gov for a free map or agridatainc.com for paid maps to get started. If soil maps in your area aren’t very detailed, you might need to map zones with a 4-wheeler and soil samples.
Overlay soil maps with yield maps, but be mindful that you’re using the right kind. “We always want to use an equal area legend [which can also be called equal point],” Beutke says. Ensure you have a well-calibrated machine within 3% of scale and with well-defined maps.
Another tool you can use to help create zones is aerial imagery. Make sure you’re using a provider with good resolution. Beutke works with 1-meter resolution, but have seen as poor as 30-meter resolution. With poorer resolution, it’s more difficult to highlight specific areas of fields to create zones. “And make sure you get the raw data,” Beutke says.
Finally, using NDVI to measure biomass [vegetative health] can be another valuable resource to overlay as you create zones. Do this just prior to tassel for the best results or prior to drydown or troubleshooting.
As you create zones, understand the following:
- Soil type/structure.
- Cation exchange capacity.
- Organic matter.
- Water holding capacity.
Creating zones is something you’ll likely fine-tune for a few years before it’s just right, but catering to differences on a per-acre basis across the field can yield more dollars in your pocket.
Check out more of what farmers learned at Corn College and learn how you can take advantage of these offerings next year.