The corn stalk nitrate-N test is a method of evaluating the nitrogen (N) fertilizer program for the end of this year so adjustments may be made to the nitrogen fertilizer next year. The test indicates if the corn was over fertilized, under fertilized, or fertilized correctly. If the corn crop in under fertilized with nitrogen, the corn will display N deficiency during the growing season. Therefore, the test is best used to determine if excess N fertilizer was used.
How to sample:
Stalk samples should be taken anytime between one and three weeks after black layer formation. Take an 8-inch length of stalk starting the segment at 6 inches above the soil surface. Remove the leaf sheaths. Avoid diseased or insect damaged stalks. Combine or composite 15 stalks into one sample per sampling area (field). Bundle the stalks together with twine, tape or wire. Place in a cardboard box and send to Ward Laboratories. Do not place stalks in plastic bags.
Analysis:
Have the stalk samples analyzed for nitrate.
Currently the cost of testing for nitrate-N is $6.60 per sample.
If results are low or excessive, conduct a thorough review of the
nitrogen fertilization program to determine where improvements can be
made.
Interpretation:
| Stalk Nitrate-N ppm N | Plant N Status | Management Suggestions |
| 0-700 | Low | Increase N for next year |
| 700-2000 | Optimal |
Yields are not limited |
| Greater than 2000 | Excess |
N fertilization or availability
Greater than needed |