The Agronomists, Ep 97: Love your soil microbes with Drs. Kari Dunfield and Bobbi Helgason
by RealAgriculture Agronomy Team
Soil is alive and full of billions (yes billions) of fungi, bacteria, protozoa and more, performing key soil functions such as nutrient cycling, creating pores, and adding stability to soil structure.
But how much do we understand of our soils? And can we take steps to love these good bugs and get rid of the baddies? To explore what lies beneath, this episode of The Agronomists features Dr. Kari Dunfield, with the University of Guelph, and Dr. Bobbi Helgason, with the University of Saskatchewan.
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Can soil microbiologists pick their favourite microbes? Not a chance
Why? Because soil microbes are so cool
Let’s scratch the surface (see what I did there) of the soil microbiome
Billions of beasts below!
Bacteria, fungi, nematodes, protozoa, all sorts of fun things
Each has a role and function and some are detrimental to plants (pathogens) but many are not
It’s a food web! Starts with the plant bringing energy down from the sun
The microbes below interact with the plant, plant roots, soil particles, chemistry and each other
It’s complicated, y’all
Soil particles themselves play a role, and soil aggregates are created by microbes
Sticky stuff from microbes is what creates pores and spaces
What about chemistry? Salinity!
Distribution sand, silt, clay. Clay is reactive, sand is less reactive
Tillage and soil is complicated
Tillage changes populations
Some additions cause feeding frenzies!
Then populations crash, and rebuild. It’s dynamic
Great question: should we strive for more abundant soil microbes or different types?
Both? Think of the soil microbe population as an engine, the total quantity determines the overall capacity, but the individuals are like cylinders, and all aren’t needed at all times
It does matter that certain ones ARE there, though
Soil your undies! Great way to measure soil microbe activity levels
Types and number changes
It’s more complicated, too, as the main driving factor for soil microbe levels was the presence of living roots/plants
We know rotation makes better soil, but why?
Balanced nutrition and different plant sources. Yes, there are differences in quality of carbon sources. Mind blown.
The functionality of the microbes is super key
Microbes don’t work alone
You need different types to perform all the functions, no one microbe does it all
Adding organic material matters. Manure is a great option
Food is food, and manure contains lots of great carbon for microbes
Does one plus one equal three?
Soil microbiomes can be tricky and challenge the expectations/assumptions
Old rules of thumb, for example, evolve as we have better diagnostic tools
Fungal dominance in no-till is not necessarily true, for example
The food source, having a plant there, makes a huge difference
There may be more fungal substance in no-till soils, but it’s not all functioning/alive
What about pH?
The extremes of pH, very little can survive
Wetter, lower pH can favour fungicides
Temperature and moisture drive populations and cycles
Exudates — do roots “recruit” microbes?
Yes, but we don’t fully understand the process or the how/why
Sugar will attract all sorts, but not specific microbes
The very simple, all the way to two-way signalling systems
It actually takes three to tango — plant, soil, microbes
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