Nitrogen: Corn’s Most Intense Nutrient

Nitrogen Cycle - Cornell

Some call nitrogen the most important nutrient, but any nutrient in short supply will limit yield.  I like to call nitrogen the most intense nutrient because having the right supply at the right time can be difficult.  Here is why:

  • Soil nitrogen tests can be extremely variable across a field at any given time
  • Soil nitrogen tests are expensive
  • Nitrogen leaches (it moves rapidly down through the soil profile with water)
  • Nitrogen volitilizes (it becomes a gas and is released into the atmosphere when hot/dry)
  • Denitrification is loss to bacteria in anerobic environments (wet soils)
  • Immobilization of nitrogen occurs when soil microbes use the mineral to digest dead plant matter (paying the carbon penalty)
  • Mineralization is when those soil microbes reach the end of their life cycle and die, releasing the nitrogen back for plant availability

v5 corn close

Nitrogen management in corn is a big subject and much can be said, but for my purposes here I only want to highlight a few important management practices that I use to deal with minimizing nitrogen waste while maximizing yield.  Ken Ferrie’s Corn College is where I learned some of how to calculate and study to develop my particular nitrogen needs, plans, and emergency options.

  • Carefully calculate how much nitrogen a crop will need based on yield history, accounting for known variables and considering the costs and benefits of the risk involved in having too much or too little.
  • Take some nitrogen tests in a few fields under different conditions to learn how to guess the rest of the acres by management zones.
  • Estimate the amount of plant matter in each field from the previous crop and pre-season weeds to assess the “carbon penalty” that needs to be paid at planting. A previous crop of corn will leave more residue, requiring 40-70 pounds of pre-plant nitrogen to be applied.  This penalty will be credited back to the crop gradually over the next few weeks as the microbes die.
  • Divide the crop’s estimated nitrogen needs into multiple applications to avoid leaching.  Apply most nitrogen just before the crop’s demand begins to soar at V5 (when plants have 5 leaf collars and are usually 18-24″ tall).
  • Use nitrogen stabilization products to inhibit denitrification by the urease enzyme with products such as N-Fixx or Agrotain.
  • Re-calculate the costs and benefits of when to apply nitrogen and in what forms.
  • Consider the cost and benefits to variable rate nitrogen by zones developed from either soil types, historic yield maps, or satellite imagery.
  • Utilize irrigation pivots to apply as much of the crop’s nitrogen needs as is feasible.
  • Utilize late-season aerial applications of dry nitrogen sources in years where moisture is adequate and yield potential justifies the cost.
  • Every year in a field or two have two or three blocks for testing the effectiveness of using more or less nitrogen than the rate estimated as most efficient to prove guesswork and provide knowledge for years to come.
  • Watch for visual and tissue sampled nitrogen deficiencies during the crop year and investigate to find the cause.
  • Test fields for compaction with a steel probe through the winter and watch for problems to develop in fields in the V2-V4 stage of corn.  I have come to call this the “ugly chick” stage of corn because in no-till conditions it sometimes reminds me of that awkward stage where chicks are just getting their feathers.  Don’t worry, it will look better soon.  Maybe this ugly unevenness can be avoided with a planter-applied starter fertilizer.  I will find out.v6 corn Anson standing

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A seventh generation farmer of good soils in Henry County Tennessee, I take seriously my responsibility to care for what has been entrusted to me for this life and to teach my children diligently.

One thought on “Nitrogen: Corn’s Most Intense Nutrient”

  1. Our garden didn’t do very well this year, and I think it’s because we didn’t put any fertilizer down at the beginning of the season. Next year, I’ll be following your advice, and putting down corn fertilizer. That way, our soil has lots of nutrients, and our veggies will grow much better!

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