Fall vs spring N applications is discussed here on CT often.

I really don't care when anyone else applies their N, or if at all. But, I did find this newsletter today from OSU interesting. Newsletter copy/paste follows. Also-I wonder how many folks actually use N-Serve in the fall? I'm guessing not many any more.

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Each year after soybean harvest, producers may consider applying nitrogen in the Fall for next year's corn crop. There are two main advantages to this practice: 1) nitrogen prices may be lower in the fall than the spring; and 2) time and labor may be more available than spring. However, the big disadvantage is the greater potential for nitrogen loss. In some years this nitrogen loss may cause a yield reduction. In an 8-year study, Ohio State University scientists, Stehouwer and Johnson, showed that average corn yields were about 5% higher from spring applied anhydrous compared to fall applied at the 160 pounds of nitrogen per acre. Without a nitrification inhibitor, the difference was almost 10%. In 2006, Lentz and Mullen again compared fall and spring applied anhydrous ammonia with N-Serv and found no statistical differences between the application times. However, spring applied consistently had larger yields over the three N rates (100, 150, 200). The data would suggest that yields are larger for spring applications compared to fall but the percentage difference will depend upon the weather for a given year.

*Only use anhydrous ammonia. Besides often being the most economical source of nitrogen, it is the slowest of all nitrogen fertilizers to convert to nitrate-nitrogen.

*Apply fall nitrogen when soil temperatures stay below 50 F and will remain below 50 F. Generally this occurs after October 20, however, as of Monday October 15, soil temperatures are still averaging around 55 F in the northwest part of the state and 60 F in the western part of the state, so we are still not quite to soil temperatures conducive to nitrogen application. Cooler temperatures will reduce the activity of the bacteria that converts ammonium to nitrate-nitrogen and will decrease the degradation of the nitrification inhibitor.

Fall Applied Nitrogen for Corn Production - Edwin Lentz, Robert Mullen

In summary, fall applied nitrogen is an option for Ohio corn producers, however, since fall applied nitrogen has to remain in the soil for about six to seven months there is a great potential for nitrogen loss. To minimize these losses consider the following management practices:

*Use a nitrification inhibitor. These products delay the conversion of ammonium to nitrate-nitrogen. The duration of this delay is weather dependent. Warm weather will shorten the effectiveness of the inhibitor.

*Apply fall nitrogen only on well-drained soils. Do not fall apply on sandy ground.In summary, fall applied nitrogen is an option for Ohio corn producers, however, since fall applied nitrogen has to remain in the soil for about six to seven months there is a great potential for nitrogen loss. To minimize these losses consider the following management practices: *Use a nitrification inhibitor. These products delay the conversion of ammonium to nitrate-nitrogen. The duration of this delay is weather dependent. Warm weather will shorten the effectiveness of the inhibitor. *Apply fall nitrogen only on well-drained soils. Do not fall apply on sandy ground.