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How to take and interpret the basal stalk nitrate test

basal stalk nitrate test

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

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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