This spring has not been ideal for keeping nitrogen in your field. Robert Mullen, Extension soil fertility specialist at Ohio State University, says if your fields have lost considerable amounts of N, you might want to consider applying more.
How Do You Know If Your N Is There?
Mullen says if your soil was wet for a considerable amount of time, you should be vigilant about scouting fields for telltale signs of N stress.
- Timing - what form of nitrogen dominates
- Weather - how much rain has fallen, was the soil waterlogged, for how long, soil temperature (higher soil temperatures are more of a concern for denitrification)
- Drainage - this affects if N will be lost through denitrification or leaching
Look for the Signs
The first way to evaluate a crop for N loss is with a visual assessment, Mullen says. "Nitrogen stress causes the plant to look chlorotic (general yellowing) that is more evident on the older (lower) leaves,” he says.
A pitfall with visual assessment, Mullen says, is that N stress can look similar to water stress.
For a more detailed test, try planting a reference strip.
"The reference strip is simply an area of the field that we know is not nitrogen deficient because we have oversupplied nitrogen,” he says. "Visual comparisons are then made between the reference area and the rest of the field to evaluate nitrogen status.”
While it might be too late for a reference strip this season, Mullen says planning for one next year is a good idea.