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Spring Application Of Fertilizer N For Corn

Mar 30, 2015

By Charles Wortmann, Brian Krienke, Charles Shapiro, Tim Shaver, Gary Hergert

Nebraska Extension Soils Team

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.

Account for the value of grain relative to fertilizer N cost using UNL tools such as:

- Fertilizer Suggestions for Corn (EC117);

-the corn chapter in Nutrient Management for Agronomic Crops in Nebraska (EC155);

-the UNL corn N calculator on cropwatch.unl.edu/soils; or

-the on-line tool soiltest.unl.edu.

-Find information and decision tools at http://cropwatch.unl.edu/soils

In determining N rate, credit the previous crop if a legume, residual soil nitrate-N to at least 2-foot depth, and N from irrigation water and manure.

Nitrogen supply from applied manure is commonly under-credited and contributions in year two and three after application are substantial, especially with feedlot manure.

High clearance nitrogen applicator in the field

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

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.

Participation in the Nebraska On-farm Research Network is one way to test the benefit of alternative practices to obtain high quality, location-specific information. The Network has several trial procedures for testing N management practices being used by producers across the state, giving you an opportunity to compare your results with theirs. View research procedures and see if one of these current on-farm research projects might be a good match for your operation:

Preplant application: UNL rate, UNL - 30 lb/ac, UNL + 30 lb/ac
Preplant application: UNL rate compared to grower's rate
Preplant application: UNL uniform rate compared to variable rate application
Preplant application: Maize-N compared to grower's rate
Sidedress application: UNL rate, UNL - 30 lb/ac, UNL + 30 lb/ac
Sidedress application: PSNT rate, PSNT - 30 lb/ac, PSNT + 30 lb/ac
Sidedress application: grower's rate compared to the Maize-N rate

Project SENSE is a new Nebraska On-farm Research Network effort to assess on-the-go sensor-guided in-season N application.

Source: unl.edu