By: Extension soil fertility specialists Dan Kaiser & Fabian Fernandez
Tools for evaluating nitrogen management have provided mixed
results. Their ability to determine whether nitrogen is deficient or sufficient
in fields is often not 100% accurate. Nonetheless, tests like the basal stalk
nitrate test are useful as a report card on nitrogen management within a field,
or area of a field, within a growing season.
Proper sampling of the right section of the stalk at the
correct time is key when taking basal stalk samples. Knowing what needs to be
done before you go to the field and the limitations of the test are also
important to make sure you get the most accurate results from basal stalk
nitrate values.
Taking the basal stalk nitrate test
The basal stalk nitrate test is a diagnostic test taken at the
end of the corn growing season. Results will show how well you did with your
nitrogen management during the season. While this test won’t tell you how much
nitrogen you need to apply next year, over time it can reveal a useful picture
of your fertilizer management practices.
To collect a sample, cut an eight-inch piece of stalk,
starting six inches above the ground. This section should include the bottom
node of the plant. Remove leaves and sheath tissue. For a complete sample,
include at least 15 stalks from a given area.
Interpreting the basal stalk nitrate test
Once you’ve taken the basal stalk nitrate test, it’s time to interpret your results. Remember, this test is diagnostic, not predictive. The results will come in measurements of PPM, or parts per million. This is an indication of nitrogen availability throughout the season.
As you can see, the results give a good picture of nitrogen management in a given field and is most effective when taken over many years to gauge any trends. Use the table below for guidance on management decisions in your operation.
Table: Interpreting the basal stalk nitrate test for corn
| Nitrate-nitrogen (NO3-N) |
Level | Interpretation |
|---|---|---|
| 0-250 ppm | Low | Nitrogen was probably deficient during the growing season |
| 250-700 ppm | Marginal | It is possible that nitrogen shortage limited yield |
| 700-2000 ppm | Adequate | Yield was not limited by a shortage of nitrogen |
| 2000+ ppm | Excessive | Nitrogen rate was too high or some production factor caused a yield reduction |
For more information about the basal stalk nitrate test, visit our web page on understanding plant analysis for crops.
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