Increasing Nitrogen Rates for High Yielding Winter Wheat

Globally, wheat is one of the top three grain crops grown along with rice and corn.  Some regions are better suited for growing wheat than The Great Lakes Region, but with the right genetics, fertility and seeding practices, we can hold our own. Described in this article are ways to gain higher yield with nitrogen applications.

Using a recommendation from Charles Mansfield and Stephan Hawkins with Purdue University Extension to raise 100 bushels of wheat per acre it takes 130 pounds of nitrogen.  100 bu/ac is considered a good wheat crop, yet some of Eastern Europe is experiencing up to 200 bu/ac.  How is this possible? They start with good genetics and uniform seed.  Then it is seeded at the right rate, depth and row width.  This controls tillering, uniformity and humidity in the row during the season. 

A 200 bu/ac wheat crop may require 12-14 passes during its lifecycle.   These include seeding, fertility, pesticides, growth regulators and harvest.  For the Midwest, this does not have a positive return on investment.  So, what can the grower improve and integrate?  Wheat has a high response to nitrogen.  Most nitrogen applications for winter wheat are made as the crop is coming out of dormancy.  This is when the vegetative growth responds well to application.  However, this is a risky approach with high rates as it is very weather dependent. 

Split applying nitrogen spreads the risk of nitrogen loss to leaching and volatilization.  To make two applications, it is advisable to make the first at the usual timing or just out of dormancy and a second application at Feekes 6 and just before 7.  Sixty percent of the nitrogen is to be applied with the first application and forty percent with the second application.  A UAN, or urea ammonium nitrate, can be used as the source of nitrogen.  It is best to apply with little to no wind, a dry leaf surface and large droplet size to reduce leaf burn.

When increasing the nitrogen rate, the largest concerns are nitrogen loss and lodging.  Lodging is when the crop falls over making harvest either troublesome or impossible.  This traps moisture leading to certain diseases and the combine is not able to harvest the crop.  A growth regulator, tank mixed with the second application, can provide great results.  What they are designed to do is make the wheat plant shorter which results in less lodging. 

Growth regulators, like Trinexapac-ethyl, must be applied at the correct time.  As mentioned before, the second nitrogen pass is at Feekes 6-7, or Zadoks 31.  This is because if a regulator is applied too late, it will restrict the developing head between nodes causing a significant yield reduction. 

Even though we cannot control the weather and regionally limited in some resources for growing higher yielding winter wheat, managing rates and timing applications are two ways to achieve more yield.