Why test?

The end of season cornstalk test was developed to help evaluate the N management strategies being used on a field. Corn that has received inadequate N will remove N from the lower cornstalk and leaves during the grain filling period. On the other hand, plants that have received more N than needed to attain maximum yields, tend to accumulate nitrate-N in the lower stalks at the end of the season. Results from this test can be used to help modify and improve N management strategies on the farm in future years.

Analysis and Reporting

Results are reported in parts per million (ppm) nitrate-N on a dry matter basis. A stalk nitrate-N value below 700ppm is considered to be low, a level above 2000ppm is considered to be in excess and values between 700 and 2000ppm considered to be optimal. View a sample report.

Sampling

The test and the interpretation of the results is calibrated based on samples taken between one and three weeks after black layers have formed on about 80% of the kernels of most ears. The portion of the plant sampled is the 8-inch segment of stalk found between 6 and 14 inches above the soil. Leaf sheaths should be removed from the segments and stalks that have been damaged by insect or disease should not be used. Fifteen 8-inch samples should be collected to represent each field.

Samples should be submitted to the laboratory for analysis as soon as possible following collection. Samples should be collected and stored in paper bags and not plastic to facilitate drying and minimize the risk of molding. If the sample will not be submitted to the lab within a day of being collected it should be stored in a refrigerator but not frozen.

Additional References & Resources

• Cornstalk testing to evaluate nitrogen management