The Agronomists, Ep 71: Greg Stewart and Elizabeth Karpinchick on in-crop N for corn


We’re back with another episode of The Agronomists, and as always, we’re excited to be here.

Today’s show — hosted by Lyndsey Smith — features Greg Stewart of Maizex Seeds and Elizabeth Karpinchick of Tone Ag. The trio discusses in-crop N applications in the corn crop (and more).

The Agronomists is brought to you by ADAMA Canada, the Pest & Predators podcast, and RealAg Radio. Click here to view all the previous episodes.


  • Soil nitrate testing is important
  • The number for broadcasting N is different than what you will put down with the planter. Keep that in mind
  • What is the earliest that that top up starts, and how late would you recommend someone still top up some N on the corn crop

CLIP 1: Corn School: Cool weather calls for more sidedness nitrogen

  • In Ontario we don’t pull samples in the fall
  • Why would we be seeing relatively high soil nitrate tests in Ontario?
  • April and May wasn’t all that warm in southern Ontario, but it wasn’t necessarily all that wet, either
  • We are using the soil nitrate test to gauge where we are at. It works to give us a * guide *
  • For those acres that have a history of manure, or have a good red closer stand, there are some really high nitrate tests coming off. Do we trust this enough to pull back our nitrogen?
  • If you’ve got really high nitrates, you’ve got to trust those and pull back. There’s enough research to support this
  • High organic matter soils is where you often see high N tests
  • If you’re going to sidedress, it’s not worth it for 10 pounds
  • If we’re soil testing, we’re doing it for a reason….we have to somewhat trust the process. Not blindly, but still
  • Consider plant factors — yield expectation, plant tissue N status, NDVI
  • Weather factors — rainfall, temperature, crop heat units
  • Cropping system factors — previous crop, tillage systems, manure additions
  • Soil temperatures — soil texture, soil organic matter, soil N status
  • Nitrogen factors — price of corn/nitrogen, source of nitrogen, application method/timing

CLIP 2: How do you apply N, let me count the ways? 

  • Is this the perfect year for split applications trials in Manitoba? Depends where you are — there’s a lot of different soil types
  • Sometimes we get so excited about the concept of splitting N applications…it doesn’t always pencil out
  • This year is really the year of nitrogen
  • We’re seeding in June — should we be cutting down on fertilizer prices?
  • Tissue tests for N top ups? Do you use them? Could be used, but a soil nitrate test gives you more information
  • There’s a window for adding N, but then the crop gets so big, we simply don’t have the toils
  • How late can we go in and it still be effective?
  • You can actually put it on right up to tasseling
  • How late can you put manure on corn? There’s a lot of rules in different places — so you have to pay attention to those

Wake up with RealAgriculture

Subscribe to our daily newsletters to keep you up-to-date with our latest coverage every morning.

Wake up with RealAgriculture

Other Episodes

The Agronomists (view all)Season 3 (2022) Episode 25

Please register to read and comment.


Register for a RealAgriculture account to manage your Shortcut menu instead of the default.