PO 21. Recognize factors that influence the results of the pre-sidedress nitrogen test.

For fields with <21 ppm:

• If you took a PSNT on a field that you expected to need sidedress N (for instance, a field that received less manure than needed to meet N needs), add the extra N.
• If you took a PSNT on a field that you did not expect to need sidedress N (for instance, a field where manure application should have provided sufficient N), make sure the field actually received the planned manure application and that the field history is correctly recorded.  Check N needs with the NYS Corn N Calculator, using the lowest manure application estimates.  If the calculator still shows that no additional N is needed, organic N mineralization rates early in the season were like lower than average, but should improve once mineralization conditions improve (warm and moist soils).  The field soil will then provide sufficient N.  If the calculator shows that additional N is needed and the PSNT is <21 ppm, consider adding the extra N.