The Agronomists, Ep 54: Jordon Wade and Wes Anderson on organic matter and fertilizer interactions

(Lara de Moissac/RealAgriculture)

Building organic matter is a complicated and sometimes slow process, but you can’t build soil organic matter without carbon and biological activity. There’s some research out there to suggest that adding commercial nitrogen fertilizer to cropping systems burns through organic matter — but field level research doesn’t show the same results. What’s happening?

First time guests Wes Anderson, vice president of agronomy at Croptimistic Technology, and Jordon Wade, assistant professor of soil health at the University of Missouri, join host Lyndsey Smith to break this one down.

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SUMMARY

  • Are we “burning” through organic matter by adding nitrogen fertilizer
  • Not a new, but a persistent, conversation
  • N fertilizer or building OM, can we have both? Does this actually show up in the field and during scientific studies?
  • There’s always room for improvement with N management, but there’s not a lot of evidence that it “burns” organic matter
  • Building OM has slowly become a common question with farmers
  • It varies not only in topsoil but also to depth
  • Thinking in 3D
  • Clip #1: What Underwear Can or Cannot Tell You About Soil Health
  • Lab incubation study slides from Jordon
  • N fertilizer feeds those microbes, which the microbes then use, and OM is built
  • We’re always burning through OM but it’s like a chequing account, inputs versus outputs and in OM’s case, we want less outputs
  • Meta-analyses are awesome y’all
  • Carbon use efficiency: how much CO2 is lost by microbes as they are active
  • Adding too much N, microbes might get fat and lazy…
  • The more crop residue that we can incorporate back into the soil, the more organic matter will increase?
  • If residue is left on the soil surface, in most places no-till does help build OM, yet is stratified, but because roots aren’t exposed to oxygen and broken down through exposure, it still builds OM
  • Note: Zones 9-10 in Wes’ maps are from an area with saline-sodic soils… challenging
  • Soil health measurements, what do they tell you?
  • Strategic tillage. Not all tillage is bad… purposeful. There’s a time and a place for both tillage and no-till
  • Residue has to be added in order to build OM. Full stop
  • Is microbial diversity better or is abundance better?
  • Completely saturated soils?
  • Tillage tools: microbe homewreckers (Sticky mesh bag theory!)
  • Get that N rate dialed in, don’t worry about “burning” organic matter
  • Is there an optimum OM? Is there a ceiling? Alberta 0.8 to 88% range (muck/peat soils aren’t actually easy to farm in, they’re a high horsepower situation). Wade wouldn’t bet the whole farm, but around 6%

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