As corn varieties have developed over time, so has the amount and timing of nitrogen uptake in corn.  In research done by Tony Vyn, Professor of Agronomy, Purdue University, “modern hybrids (post-1990) took up 27 percent more total nitrogen from the soil after flowering than pre-1990 corn plants. In fact, nitrogen uptake after flowering in post-1990 hybrids averaged 56 percent of the total grain nitrogen at the end of the season.”  He also goes on to state that “post-1990 corn hybrids use nitrogen more efficiently, so less is necessary per unit of yield. But as those plants increase nitrogen utilization, they increase their uptake of other nutrients, which affects how much of those nutrients growers need to use and when they need to apply them.”

Both these statements bring forth some important questions:

  1.     Do I need to put as much nitrogen on my corn crop as I always did?
  2.     Does timing have anything to do with overall yield?

To answer this, we first need to understand when corn nitrogen uptake occurs.

The graph below from the University of Missouri Plant Sciences Department shows the timing that the uptake of nitrogen takes place.  As you can see, 40% of the nitrogen is needed from R1 (silking) to R6 (physiological maturity).

The required 40% may not always be available at the R1 stage, meaning we may not have maximized our yield potential.  Environmental conditions affect the amount of nitrogen available in the summer months. For those that apply all of their nitrogen fertilizer up front before planting, wet, rainy conditions from VE to V18 could result in lower than expected nitrogen availability and other methods of application may need to be explored.  Lately, it has become common practice to apply a portion of the total nitrogen required at planting through the planter, followed by side dressing nitrogen around the 4-5 leaf stage or V3-V4.  This prolongs the availability of nitrogen through the growing season.  There also seems to be a lot of conversation about applying a portion at the R1 stage through Y applicators or drop nozzles from high-clearance application equipment, although research is still ongoing as to if this is a viable solution.

As you can see, producers have much to consider when growing corn and managing nitrogen availability. Do some research on your own farm and monitor your crop to determine what works well for you to get the most out of your crop.  This coming summer I am planning on doing trials with growers to better understand the best and most economical methods for managing nitrogen. If you are interested in doing a trial, feel free to contact me and I will assist you in any way I can.

Chuck Belanger, Maizex Seeds Yield Specialist, North Essex and South Chatham-Kent Counties
Twitter: @sprayman63 


Ignacio A. Ciampitti and Tony J. Vyn. Grain Nitrogen Source Changes Over Time in Maize: A Review. Crop Science, 2013.,-study-shows.html

Peter C. Scharf and John A. Lory. Best Management Practices for Nitrogen Fertilizer in Missouri. IPM1027, August 2006.