There is a certain precise amount of nitrogen that your corn crop will need this year in order to achieve its yield potential. The problem is that nobody knows what it is. Another problem is that nobody can afford to guess. Money is too tight to just throw extra nitrogen on the field, and inventory is too important to go the route of allowing your sidedress rate correlate with the milk price. The good news is that there are good tools for figuring out what your sidedress rate should be!
Adapt-N and the PSNT are useful tools for predicting sidedress nitrogen needs for corn.
While Adapt-N is a great tool, you need to have a certain set of data to make it work. The good news is that if you have a current nutrient management plan, you have most of the information you need already!
In order to make the process of transferring that information from the farmer to the program (or the consulting agronomist), I have created a couple of forms that have all or most of the data necessary to make Adapt-N work. The PDF version of the form will work for those just interested in hand-writing the information. The Excel version of the form will be more useful for someone with multiple fields or fields with zones where the treatment is similar from one field or zone to another. For example, if fields 1,2, and 3 all had the same manure rates, hybrids, and planting dates, you could enter all the data that is the same for all of the fields, and then save the document under three different names, and finally enter the correct unique information into each of the respective documents.
The PSNT is a good-old standby that works most of the time. The problem is that it does not know that we have had a cool spring and that a lot of the nitrogen in the pipeline (i.e., soil organic matter) has not mineralized at the same rate it would have if temperatures were warmer. It does not know about our weather patterns. That said, the PSNT will generate a recommendation that is better than blindly guessing. Keep in mind that the PSNT should be taken only when the corn is 6-12″ tall and that the PSNT is not useful if broadcast applications of nitrogen have already been applied. Be sure to avoid taking samples near the zone where starter fertilizer was placed.