Three questions about NH3 applications for wheat
Q1: I’m in long-term no-till, but am thinking about having anhydrous ammonia applied preplant next week before wheat planting. The applicator is one of the new low-disturbance units, but I’d still like to have as much distance as possible between rows to minimize the amount of residue disturbance. What is the widest spacing you would advise for preplant anhydrous ammonia applications for wheat in 7 ½-inch rows?
A: There are a couple of ways to approach this. The easiest answer is to use a band width of 15 inches or less in this situation. In more general terms, you should ideally go no wider than twice the row spacing so all the planted rows will have direct access to an ammonia band on one side or another. That way, none of the rows of wheat will have to spread roots through another row to get to the N. A couple years ago we re-did some of this work and saw that a row of wheat that didn’t have direct access to an ammonia band (due to having another row of wheat between it and the band on both sides), was stunted and had reduced N content. For wheat in 12-inch rows, use an anhydrous band spacing of 24 inches or less, and if possible, split the rows with the anhydrous ammonia bands.
Q2: How long should you wait after an application of anhydrous ammonia before planting wheat?
A: As a general rule, wait about 7 to 10 days between the anhydrous ammonia application and wheat planting. The higher the nitrogen rates and the wider the spacing (creating a higher concentration of ammonia in the band), the longer period of time you should wait. Also, in dry soils you may need to wait longer.
Q3. If anhydrous ammonia was applied in late August for wheat, do producers still need to apply some extra N at planting time either with the seed (as part of the starter fertilizer), dribbled in a band on the surface, or broadcast on the surface?
A: It depends in part on the spacing of the anhydrous ammonia bands. If the anhydrous bands are spaced at 12 to 15 inches, extra N at planting time is probably not necessary (although it’s not a bad idea to apply a little starter that includes some N anyway, if possible). With wider band spacing and wider rows, you probably will need to make sure you apply some N at planting time, since it will take longer for the wheat roots to grow into that band.