Figure 1. In-season nitrogen application with high clearance applicators and based on actual plant need provides for efficient nutrient management for corn.
Figure 1. In-season nitrogen application with high clearance applicators and based on actual plant need provides for efficient nutrient management for corn.

Consider the following as you gear up for spring nitrogen application in corn:

The price of corn is low compared to pre-2014 harvest prices. This should affect N rate application. 

Use N-LAT (Nebraska N Loss Assessment Tool)  to estimate average N loss to leaching, volatilization, denitrification, and nitrous oxide emission, and determine the effects of alternative practices. Conditions affecting N loss vary greatly within and across fields, and N-LAT is useful for identification of the high loss areas.

Volatilization loss with surface application of urea or urea ammonium nitrate is a concern. Calcareous soil, heavy crop residue cover, and delayed rainfall following application contribute to greater loss. Consider use of a urease inhibitor if risk of loss is relatively high (i.e., as determined by N-LAT). Rainfall or irrigation of 0.25 to 0.50 inch is sufficient to move the urea into the soil and greatly reduce potential N loss.

If weather conditions delay N application, give priority to timely planting. The N can be applied after planting.

Germinating seed and emerging plants near a shallow band of spring-applied anhydrous ammonia can cause seedling damage. Avoid planting near such bands.

If more than 50% of the crop residue was removed in a continuous corn cropping system, corn yield potential in irrigated or Corn Belt fields may remain the same or increase. Preliminary research shows that N rate can be reduced by 20 lb N per acre and not affect yield, because of less immobilization of fertilizer N by microbes breaking down crop residue; this is not yet confirmed.

Nitrogen use efficiency can generally be improved by side-dress application or fertigation of most of the N in-season such as at the 8-leaf stage or later.

  • Apply up to 75 lb N/acre pre-plant, a total of fall and spring application.
  • Apply in-season to meet crop needs according to the:

     — balance of the UNL recommendation;
     — pre-sidedress nitrate test (PSNT) (see PSNT article in CropWatch); or
     — use of handheld reflectance sensor, or on-the-go sensing and application; these require a reference area with a high pre-plant N  application for most efficient use.