Management zones are the foundation of a good soil fertility program. Uniform fields are a rarity, and growers need to manage land according to soil variability.
Missy Bauer, B&M Crop Consulting, offered a management zone roadmap at Corn College 2014 in Coldwater, Mich. "If we’ve got management zones, what can we use them for? There are different soils across the same field and we need to treat that field accordingly."
Bauer applies treatments – lime or potash for example – based on what different areas of a field need. Management zones allow application based on what soil tests reveal those areas require. "Once I’ve got a good foundation and soil fertility is not a yield-limiting factor, then I have the opportunity for variable rate corn populations and nitrogen," she says. "I can also look at it as trying to fine-tune water management from tile drainage or irrigation. It really helps with scouting and pest problems as well."
What determines how much population she plants in a given field? Water holding capacity. "How many plants can a field support? If I want variable rate population across a field, I want to know what the CEC and organic matter is of the zones. I want that information and it’s found in my soil tests."
Once management zones are created, soil samples should be pulled from within the zones. Brad Beutke, Crop-Tech Consulting, Heyworth, Ill., echoes Bauer on the benefits of management zones: "We want to get away from the traditional grid-based system that most agronomists and universities have been using the last several years. We’re strong proponents of the management zone based system in order to implement a soil-testing program and a variable rate program."
Management zones are also key for nitrogen management. Contrary to conventional wisdom, Bauer says a producer’s good ground often doesn’t need much fertilizer nitrogen, and conversely, poor ground often needs more help. "That’s the opposite of what most people think or what they’re taught from the university side of things when you’re looking at pounds of N per bushel of corn."
Regarding variable rate planting populations, plant spacing must be perfect and good ear counts demand uniformity. "If you’re a train wreck with your plant spacing, then don’t try it because you’ll change your populations, but you’ll never change your ear counts," says Bauer.
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