‘I’ll never apply fall nitrogen again!’
I’ve heard several growers exclaim that they will never fall-apply nitrogen again. Although fall-applied fields often suffered more loss than spring-applied fields, that is not always the case.
Growers who applied late in the fall when recommendations would suggest it was safer are more satisfied with their results than those who were early. For those who cannot recall our recommendations for fall nitrogen timing, here they are again:
• Do not fall-apply N on soils that typically flood in the spring or to soils with sandy loam or coarser textures.
• Do not even think about applying anhydrous ammonia until Oct.1.
• After Oct.1, check the soil temperature at a 4-inch depth from 6 to 8 a.m. When it hits 50 degrees F, it is practical to apply anhydrous ammonia (but not urea!).
• A week after the date for anhydrous ammonia, growers can start applying banded urea.
• Two weeks after the date for anhydrous ammonia, growers can start broadcast-incorporating urea.
This past season, the soil temperature dropped to 50 degrees F about Oct. 15. That means that banded urea application should not have begun until Oct. 22 and broadcast urea until Oct. 29.
• There’s nothing wrong with a well-timed nitrogen application in the fall.
• Don’t apply N when soil temperatures are above 50 degrees F.
• N inhibitor shouldn’t be used to move up the application date.
I know that a great deal of fall N was applied before these dates. I traveled to Bismarck about Sept. 20, and there was a grower applying anhydrous ammonia to a field near Jamestown. I also saw urea applicators in the field about the same time in the valley. This was a very bad plan.
There is nothing wrong with well-timed fall N application in North Dakota. In years of dry weather, it didn’t matter when nitrogen was applied. If the last 18 years of wetness is an indication of the beginning of a trend, I think that this winter and spring will also be wet, and we will be set up for losses for N that was applied too early.
Agronomy does not always mesh with convenience. Although many growers have a “harvest gap” in September after small-grain harvest and before soybeans, corn and sunflower, it is not the time to fall-apply N. Phosphorus and potassium can be applied during this time, but not N. Too many bad things can happen to early-applied N.
A nitrification inhibitor should be used not to move the date of application earlier, but to protect the N applied at a safer date from unanticipated losses from early-spring wetness. N-Serve can be applied with anhydrous ammonia to protect N from losses due to nitrification in the fall or spring. Instinct is an encapsulated form of nitrapyrin (the active ingredient in N-Serve). The label I have lists it as a spring additive with urea or UAN. Check with your Dow AgroSciences representative to see if it is labeled for fall application with urea.
Franzen is a North Dakota State University Extension soils specialist.
WAIT TO APPLY: Don’t apply N too soon this fall. Soil temperatures should be lower than 50 degrees F to reduce the risk of losses.
This article published in the September, 2011 edition of DAKOTA FARMER.
All rights reserved. Copyright Farm Progress Cos. 2011.