Preplant Banding Ammonia & Urea in Corn

A very efficient placement method for rates of nitrogen that can’t be placed at seeding is the preplant band. Despite the popularity of direct or one-pass seeding this is still used in crops where some pre-plant tillage is done – like for corn.

The past few years, more often in dry springs, I have seen stand thinning using this practice. When the corn row falls directly over the N band (be it ammonia or urea), seedlings are injured, stunted and sometimes killed. This leaves a repeating pattern in an angle across the field.

There are some standard guidelines if using this practice:

  • Stand thinning may occur where the seed row intersects the N band. Band N on an angle so that it intersects just a short length of row.  OR if the injection placement can be controlled with accurate GPS guidance positioning technology, split with the future corn row.  Six inch separation should be sufficient.
  • Place the nitrogen deep. Banding at 3” depth may be sufficient for slot closure and N retention in the soil – but this will only be an inch or so below the seed. The original guideline calls for 4” vertical separation of injection point and seed.
  • The toxicity will be worse under dry conditions and on sandier soils.
  • Waiting a certain period of time offers only a slight increase in safety.  Injury can still occur even if planting is delayed for a considerable period of time.
  • Increasing plant populations to account for such thinning will not eliminate the appearance of gaps in the row.

Figure 1 is of corn thinning over a preplant urea band.

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Figure 1: Corn thinning over a preplant urea band (Photo by John Heard, Manitoba Agriculture)

Figure 2 is of corn seedling based on their proximity in intersecting the shallow placed preplant ammonia band.

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Figure 2: Impact of shallow placed preplant ammonia band on corn seedlings (Photo by John Heard, Manitoba Agriculture)

Submitted by: John Heard, Crop Nutrition Specialist, Manitoba Agriculture

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