The Agronomists, Ep 91: John Heard, Peter Johnson, and Greg Stewart on managing N losses

(Debra Murphy/RealAgriculture)

Managing nitrogen fertilizer is a balancing of economic considerations, yield goals, and environmental implications.

With both increased fertilizer prices and scrutiny on N fertilizer emissions, this episode of The Agronomists tackles the loss pathways and management tools required to minimize them.

Our experts for this conversation are John Heard of Manitoba Agriculture, Peter Johnson of RealAgriculture, and Greg Stewart of Maizex.

This episode of The Agronomists is brought to you by ADAMA Canada, Decisive Farming by Telus Agriculture, CanolaMasters, and Disruptors, an RBC podcast.

Catch a new episode of The Agronomists every Monday night at 8 pm E!

 

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SUMMARY

  • We begin this show with a detailed description of the nitrogen loss pathways, by way of a plumbing pipe analogy (stick with us, it makes perfect sense)
  • At every step of the N movement pipeline, from addition to loss, use, or immobilization, there are factors to consider on what will put nitrogen at risk
  • For every pound of nitrogen applied, only 40 to 60 per cent gets to the plant, but the balance is not necessarily lost or an emission — N can leave as N2 gas (not a GHG), can be tied up in organic material or soil microbes, as well as leach or gas off. Not mentioned, but it can also be used by weed species, too!
  • It should be noted there will be no clips tonight as we try and cover as much on this topic as we can
  • Each type of loss can be managed to some extent, but it is a combination of application and incorporation equipment, the use of enhanced efficiency fertilizers where applicable, soil conditions and time of year, plus more variables
  • For the west and east, there are some different concerns: in the west “loitering N” is more common management consideration
  • Loitering N can be lost to denitrificaiton or leaching
  • What about cover crops? Two questions: one, is there value in soil testing ahead of the cover crop, and, two, how do we measure what the cover crop is holding or tie-ing up? When is it released?
  • Let’s look at a case study!
  • Ways to minimize losses in a split-app system? Widen the splits (i.e. don’t front load as much), use a urease inhibitor where surface applied or shallow incorporated, move more deeper in the soil
  • Strip tillage offers some options for N management, including putting N in the strip. But not all strip tillage is created equal: beware too-high of rates in the strip!