How much N should you apply? When it was cheap, a lot was applied. When it became expensive, less was applied, and some fields did not get any N the past several years. However the question of application rate should be a function of soil type, moisture, the price of corn and the price of the N. Those factors are all included in a decision aid calculator. Fernandez says split your application between fall and spring, “it is important to remember that it is not necessary to make the entire application in the fall. Some producers might find it beneficial for their production system to apply a portion of the total rate in the fall and reserve the rest for a later application in spring.”

 

Any final Fernandez tips to make the most of your nitrogen dollar?

1) Application in the spring, close to the time of rapid uptake, maximizes yield because there is less chance for leaching or denitrification.

2) Most often, though, under normal spring conditions there is little or no difference between fall and spring times of application.

3) Fall applications have both economic and logistic advantages. Soil conditions are typically more conducive to application, there is more time available than during the busy planting season, equipment and labor are better distributed, and often there are price incentives to buy anhydrous ammonia.

4) The spring typically is wet, and soil compaction, especially for manure application, is of greater concern. Also, waiting until spring to apply fertilizer can delay planting, damage crops, and delay application of fertilizer to meet early nutrient uptake needs of the crop.

5) If you don't like taking big risks but a fall application makes sense, it may be better to apply part of the N in the fall and wait until spring to apply the rest.

 

Summary

Fall application of N should wait for soil temperatures at the 4-in. market to drop below 50º F. Do not apply nitrate containing fertilizers because of the potential for leakage, since nitrates are a form of ammonia which does not bind with soil particles. Make a split application of N between fall and spring, to take advantage of time in the fall, but also ensure some of it will be available at the time of crop uptake.