Just a start
Following Best Management Practices advisories on N application is only the beginning of reducing your field nitrate losses, says Matt Helmers, ISU associate professor, agricultural and biosystems engineering.Better in-field nutrient management alone can’t do the job. “The right application of nitrogen (N) is the first step,” he says. “But even then, N concentrations in drainage water are still higher than where we want to be.”
Fortunately, research advances offer a toolkit of options that, combined, may achieve such rates.
Helmers cites experiments that found nitrate levels at 5-10 part per million (ppm) in tile runoff even when N had not been applied, and levels well above 10 ppm after it was applied at 150-160 lbs./acre to corn in a corn-soybean rotation.
“How much we can reduce nitrate loss by applying the right amounts at the right time depends on where we’re starting, and that’s something we don’t know yet. If we are at 200 lbs. and cut back to 130, we could get a 30% drop in nitrate loss, but if we’re cutting from 150 lbs. to 125, we might only see a 15% decline,” he says.
Complicating nitrate-loss prevention is the wide diversity of soil types, weather patterns and cropping approaches across the Corn Belt. That means a “one size fits all” mandate won’t work.