Nitrogen (N) management is one of the most challenging areas in corn production because of the many factors that influence N availability including: form of N applied, timing of application, impact of weather, etc. This is especially true when manure is part of the system. Standard N recommendations take into account many of these variables and early in-season tests such as the Pre-sidedress Soil Nitrate Test (PSNT) and Chlorophyll Meter test are very helpful in reducing the uncertainty in N recommendations. While this uncertainty can never be completely eliminated, it can be minimized. A key to improving N management over time is having reliable feedback on how well your N management program is working. While good yields and dark green plants are clear indicators of adequate N, they do not tell you if you have too much N which can especially be a problem for fields to which manure has been applied. Similarly, visual symptoms of N deficiency may be observed late in the season, but they are not always associated with decreased crop yields.
The Late Season Cornstalk Nitrate Test has been demonstrated to be a reliable end-of-season indicator of crop N status based on research performed throughout PA as well as other states. It provides a good assessment of whether the crop had the right amount of N or too much N or whether it ran out of gas. This information combined with records of N management can be very useful for making future management decisions. While you could test all fields, testing a few representative fields will probably be adequate to provide a good assessment of your N program.
To perform this test, print the submission form and sampling instructions Sampling instructions should be followed carefully. Send the completed submission form and samples with payment to the Agricultural Analytical Services Laboratory.